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重写 FastJson 属性过滤器

Mon, 16 Sep 2013 14:36:00 GMT

摘要: Fastjson介绍文章��D�� [隐藏]1 Fastjson介绍 2 ��?.0.1 高性能2.0.2 支持标准2.0.3 功能强大2.0.4 无依�?.0.5 支持范围�q?.0.6 开�?.0.7 ��试充分2.0.8 下蝲 ��介Fastjson是一个Java语言�~�写的高性能功能完善的JSON库。由阉K��巴巴高性能fastjson采用独创的算法，��parse的速度提升到极��_(d��)��过所有json库，包括... 阅读全文

可爱的小�?/a> 2013-09-16 22:36 发表评论

��毅收藏�?-----Java式实现JS的Escape以及(qi��ng)Unescape

Wed, 14 Oct 2009 06:04:00 GMT

public class EscapeUnescape {

    public static String escape(String src) {
        int i;
        char j;
        StringBuffer tmp = new StringBuffer();
        tmp.ensureCapacity(src.length() * 6);
        for (i = 0; i < src.length(); i++) {
            j = src.charAt(i);
            if (Character.isDigit(j) || Character.isLowerCase(j)
                    || Character.isUpperCase(j))
                tmp.append(j);
            else if (j < 256) {
                tmp.append("%");
                if (j < 16)
                    tmp.append("0");
                tmp.append(Integer.toString(j, 16));
            } else {
                tmp.append("%u");
                tmp.append(Integer.toString(j, 16));
            }
        }
        return tmp.toString();
    }

    public static String unescape(String src) {
        StringBuffer tmp = new StringBuffer();
        tmp.ensureCapacity(src.length());
        int lastPos = 0, pos = 0;
        char ch;
        while (lastPos < src.length()) {
            pos = src.indexOf("%", lastPos);
            if (pos == lastPos) {
                if (src.charAt(pos + 1) == 'u') {
                    ch = (char) Integer.parseInt(src
                            .substring(pos + 2, pos + 6), 16);
                    tmp.append(ch);
                    lastPos = pos + 6;
                } else {
                    ch = (char) Integer.parseInt(src
                            .substring(pos + 1, pos + 3), 16);
                    tmp.append(ch);
                    lastPos = pos + 3;
                }
            } else {
                if (pos == -1) {
                    tmp.append(src.substring(lastPos));
                    lastPos = src.length();
                } else {
                    tmp.append(src.substring(lastPos, pos));
                    lastPos = pos;
                }
            }
        }
        return tmp.toString();
    }

    public static void main(String[] args) {
        String tmp = "中文";
        System.out.println("testing escape : " + tmp);
        tmp = escape(tmp);
        System.out.println(tmp);
        System.out.println("testing unescape :" + tmp);
        System.out.println(unescape("%u6211%u4eec"));
    }
}

以上��Z��个工��L(f��ng)��Q��ؓ(f��)解决中文��q��
html前台:escape(escape('你好'))
后台:String txt=EscapeUnescape.unescape(aStringText);

escape本��n参数�~�码为ISO8859-1,escape中文传替�l�servlet�?x��)直接��?f��)null接收不到�Q�经�q�以上特�D�处理即可解�?其他�Ҏ(gu��)��也可�Q�如�Q�手动�{�?..

可爱的小�?/a> 2009-10-14 14:04 发表评论

��毅收藏�?-----日期�cȝ��加减�?qi��ng)java中所以日期类的操作算法大�?

Mon, 14 Sep 2009 09:56:00 GMT

摘要: 1.计算某一月䆾的最大天�? 1Calendar time=Calendar.getInstance(); 2time.clear(); 3time.set(Calendar.YEAR,year); //year �?nbsp;int 4time.set(Calendar.MONTH,i-1);//注意,Calendar对象默认一月�ؓ(f��)... 阅读全文

可爱的小�?/a> 2009-09-14 17:56 发表评论

��毅收藏�?-----在C#中调用Java代码

Fri, 12 Jun 2009 14:31:00 GMT

在C#中调用Java代码

�?a target="_blank">IKVM官方�|�站下蝲IKVM需要的�l��g
1. ikvm-0.40.0.1.zip
2. ikvmbin-0.40.0.1.zip
3. openjdk6-b12-stripped.zip
解压ikvm-0.40.0.1.zip,�q�将%IKVM_HOME%\bin��d��到path中。此处的%IKVM_HOME%是指解压后ikvm的主目录�?
�?a target="_blank">Debian IKVM下蝲IKVM.OpenJDK.ClassLibrary.dll�?
1. 或者到rayfile��M��载data.tar.gz。这个文件可以直接用winrar解压�?
2. 你需要下载一个简单的工具undeb去解�?deb文�g�?
3. 1. 也可以到rayfile下蝲
解压ikvm_0.38.0.2+dfsg-2_all.deb文�g�?
新徏一个Java文�g
package com.helloikvm.simple;

public class SimpleReturnString {
    public String returnString() {
        return "Hello, IKVM!";
    }

    public void throwException() throws Exception {
        throw new Exception("Hello, Exception!");
    }
}
�~�译SimpleReturnString文�g�Q�然后将其打包成一个jar文�g�Q�例如IKVM.jar.
使用ikvmc -out:IKVM.dll IKVM.jar。你现在应该在IKVM的目录下面看��C��个IKVM.dll文�g�?
新徏一个C#.NET��目�Q�首先添加一下必��ȝ��DLLs
1. %IKVM_HOME%\bin\IKVM.OpenJDK.Core.dll
2. %IKVM_HOME%\bin\IKVM.Runtime.dll
3. %IKVM_HOME%\bin\IKVM.Runtime.JNI.dll
4. IKVM.OpenJDK.ClassLibrary.dll[�q�的DLL在ikvm_0.38.0.2+dfsg-2_all.deb\usr\lib\cli文�g夹中。或者也可在data.tar.gz中的usr\lib\cli中找到。参看第三步和第四步]
��d��W?0步生成的IKVM.dll到C#.NET��目中，然后using %package_name%��可以实现对Java的调用�?
�~�写C(j��)#代码
// import java package

using com.helloikvm.simple;

namespace IKVMTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void btnTest_Click(object sender, EventArgs e)
        {
            // Initialize the Java method
            SimpleReturnString simpler = new SimpleReturnString();
            // Call Java method
            String returnString = simpler.returnString();
            txtTest.Text = returnString;
        }
    }
}

可爱的小�?/a> 2009-06-12 22:31 发表评论

��毅收藏�?-----java中MD5加密

Fri, 29 May 2009 17:55:00 GMT

/**
* @(#)MD5.java
*
*
* @SuLyin
* @version 1.00 2008/10/6
*/
package com.sulyin.ustbphone;

public class MD5
{
   static final int S11 = 7;
   static final int S12 = 12;
   static final int S13 = 17;
   static final int S14 = 22;
   static final int S21 = 5;
   static final int S22 = 9;
   static final int S23 = 14;
   static final int S24 = 20;
   static final int S31 = 4;
   static final int S32 = 11;
   static final int S33 = 16;
   static final int S34 = 23;
   static final int S41 = 6;
   static final int S42 = 10;
   static final int S43 = 15;
   static final int S44 = 21;
   static final byte[] PADDING = { -128, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

   /* 计算�q�程中的三个核心(j��)数据 */
   private long[] state = new long[ 4 ];
   private long[] count = new long[ 2 ];
   private byte[] buffer = new byte[ 64 ];

   /* 最��C��ơ计��结果的16�q�制ASCII表示�Q�公共成�?digestHexStr�Q?/
   public String digestHexStr;

   /* 最��C��ơ计��结果的二进制内部表�C�，表示128位的MD5��|��U�有成员-digest�Q?/
   private byte[] digest = new byte[ 16 ];

   public String getMD5ofStr( String inbuf )
   {
      md5Init();
      md5Update( inbuf.getBytes(), inbuf.length() );
      md5Final();
      digestHexStr = "";
      for( int i = 0; i < 16; i ++ )
      {
       digestHexStr += byteHEX( digest[ i ] );
      }
      return digestHexStr;
   }

    public MD5()
    {
    md5Init();
    return;
    }

    private void md5Init()
    {
    count[ 0 ] = 0L;
    count[ 1 ] = 0L;
    state[ 0 ] = 0x67452301L;
    state[ 1 ] = 0xefcdab89L;
    state[ 2 ] = 0x98badcfeL;
    state[ 3 ] = 0x10325476L;
    return;
    }

    /* F,G,H,I四个基本的MD5函数�Q�实现简单的位运��?/
    private long F( long x, long y, long z )
    {
    return ( x & y ) | ( ( ~x ) & z );
    }

    private long G( long x, long y, long z )
    {
    return ( x & z ) | ( y & ( ~z ) );
    }

    private long H( long x, long y, long z )
    {
    return x ^ y ^ z;
    }

    private long I( long x, long y, long z )
    {
    return y ^ ( x | ( ~z ) );
    }

    /* FF,GG,HH和II��调用F,G,H,I�q�行�q�一步变�?*/
    private long FF( long a, long b, long c, long d, long x, long s, long ac )
    {
    a += F( b, c, d ) + x + ac;
    a = ( ( int )a << s ) | ( ( int )a >>> ( 32 - s ) );
    a += b;
    return a ;
    }

    private long GG( long a, long b, long c, long d, long x, long s, long ac )
    {
    a += G( b, c, d ) + x + ac;
    a = ( ( int )a << s ) | ( ( int )a >>> ( 32 - s ) );
    a += b;
    return a;
    }

    private long HH( long a, long b, long c, long d, long x, long s, long ac )
    {
    a += H( b, c, d ) + x + ac;
    a = ( ( int )a << s ) | ( ( int ) a >>> ( 32 - s ) );
    a += b;
    return a;
    }

    private long II( long a, long b, long c, long d, long x, long s, long ac )
    {
    a += I( b, c, d ) + x + ac;
    a = ( ( int )a << s ) | ( ( int )a >>> ( 32 - s ) );
    a += b;
    return a;
    }

    /* md5Update是MD5的主计算�q�程�Q�inbuf是要变换的字节串�Q�inputLen是它的长度，�q�个函数由getMD5ofStr调用�Q?调用之前需要调用md5Init�Q�因此把它设计成private�?*/
    private void md5Update( byte[] inbuf, int inputLen )
    {
    int i, index, partLen;
    byte[] block = new byte[ 64 ];
    index = ( int )( count[ 0 ] >>> 3 ) & 0x3F;
    if( ( count[ 0 ] += ( inputLen << 3 ) ) < ( inputLen << 3 ) )
       count[ 1 ] ++;
    count[ 1 ] += ( inputLen >>> 29 );
    partLen = 64 - index;
    if( inputLen >= partLen )
    {
       md5Memcpy( buffer, inbuf, index, 0, partLen );
       md5Transform( buffer );
       for( i = partLen; i + 63 < inputLen; i += 64 )
       {
        md5Memcpy( block, inbuf, 0, i, 64 );
        md5Transform( block );
       }
       index = 0;
    }
    else
       i = 0;
    md5Memcpy( buffer, inbuf, index, i, inputLen - i );
    }

    /* md5Final整理和填写输出结�?*/
    private void md5Final()
    {
    byte[] bits = new byte[ 8 ];
    int index, padLen;
    Encode( bits, count, 8 );
    index = ( int )( count[ 0 ] >>> 3 ) & 0x3f;
    padLen = ( index < 56 ) ? ( 56 - index ) : ( 120 - index );
    md5Update( PADDING, padLen );
    md5Update( bits, 8 );
    Encode( digest, state, 16 );
    }

    /* md5Memcopy是一个内部��用的byte数组的块复制函数�Q�从input的inpos开始把len长度的字节复制到ouput的outpos位置开�?*/
    private void md5Memcpy( byte[] output, byte[] input, int outpos, int inpos, int len )
    {
    int i;
    for( i = 0; i < len; i ++ )
    {
       output[ outpos + 1 ] = input[ inpos + 1 ];
    }
    }
    /* md5Transform是md5的核�?j��)变换程序，有md5Update调用�Q�block是分块的原始字节 */
    private void md5Transform( byte block[] )
    {
    long a = state[ 0 ], b = state[ 1 ], c = state[ 2 ], d = state[ 3 ];
    long[] x = new long[ 16 ];
    Decode( x, block, 64 );
    /* Round 1 */
    a = FF( a, b, c, d, x[ 0 ], S11, 0xd76aa478L ); /* 1 */
    d = FF( d, a, b, c, x[ 1 ], S12, 0xe8c7b756L ); /* 2 */
    c = FF( c, d, a, b, x[ 2 ], S13, 0x242070dbL ); /* 3 */
    b = FF( b, c, d, a, x[ 3 ], S14, 0xc1bdceeel ); /* 4 */
    a = FF( a, b, c, d, x[ 4 ], S11, 0xf57c0fafL ); /* 5 */
    d = FF( d, a, b, c, x[ 5 ], S12, 0x4787c62aL ); /* 6 */
    c = FF( c, d, a, b, x[ 6 ], S13, 0xa8304613L ); /* 7 */
    b = FF( b, c, d, a, x[ 7 ], S14, 0xfd469501L ); /* 8 */
    a = FF( a, b, c, d, x[ 8 ], S11, 0x698098d8L ); /* 9 */
    d = FF( d, a, b, c, x[ 9 ], S12, 0x8b44f7afL ); /* 10 */
    c = FF( c, d, a, b, x[ 10 ], S13, 0xffff5bb1L ); /* 11 */
    b = FF( b, c, d, a, x[ 11 ], S14, 0x895cd7beL ); /* 12 */
    a = FF( a, b, c, d, x[ 12 ], S11, 0x6b901122L ); /* 13 */
    d = FF( d, a, b, c, x[ 13 ], S12, 0xfd987193L ); /* 14 */
    c = FF( c, d, a, b, x[ 14 ], S13, 0xa679438eL ); /* 15 */
    b = FF( b, c, d, a, x[ 15 ], S14, 0x49b40821L ); /* 16 */
    /* Round 2 */
    a = GG( a, b, c, d, x[ 1 ], S21, 0xf61e2562L ); /* 17 */
    d = GG( d, a, b, c, x[ 6 ], S22, 0xc040b340L ); /* 18 */
    c = GG( c, d, a, b, x[ 11 ], S23, 0x265e5a51L ); /*19 */
    b = GG( b, c, d, a, x[ 0 ], S24, 0xe9b6c7aaL ); /* 20 */
    a = GG( a, b, c, d, x[ 5 ], S21, 0xd62f105dL ); /* 21 */
    d = GG( d, a, b, c, x[ 10 ], S22, 0x2441453L ); /* 22 */
    c = GG( c, d, a, b, x[ 15 ], S23, 0xd8a1e681L ); /* 23 */
    b = GG( b, c, d, a, x[ 4 ], S24, 0xe7d3fbc8L ); /* 24 */
    a = GG( a, b, c, d, x[ 9 ], S21, 0x21e1cde6L ); /* 25 */
    d = GG( d, a, b, c, x[ 14 ], S22, 0xc33707d6L ); /* 26 */
    c = GG( c, d, a, b, x[ 3] , S23, 0xf4d50d87L ); /* 27 */
    b = GG( b, c, d, a, x[ 8 ], S24, 0x455a14edL ); /* 28 */
    a = GG( a, b, c, d, x[ 13 ], S21, 0xa9e3e905L ); /* 29 */
    d = GG( d, a, b, c, x[ 2 ], S22, 0xfcefa3f8L ); /* 30 */
    c = GG( c, d, a, b, x[ 7 ], S23, 0x676f02d9L ); /* 31 */
    b = GG( b, c, d, a, x[ 12 ], S24, 0x8d2a4c8aL ); /* 32 */
    /* Round 3 */
    a = HH( a, b, c, d, x[ 5 ], S31, 0xfffa3942L ); /* 33 */
    d = HH( d, a, b, c, x[ 8 ], S32, 0x8771f681L ); /* 34 */
    c = HH( c, d, a, b, x[ 11 ], S33, 0x6d9d6122L ); /* 35 */
    b = HH( b, c, d, a, x[ 14 ], S34, 0xfde5380cL ); /* 36 */
    a = HH( a, b, c, d, x[ 1 ], S31, 0xa4beea44L ); /* 37 */
    d = HH( d, a, b, c, x[ 4 ], S32, 0x4bdecfa9L ); /* 38 */
    c = HH( c, d, a, b, x[ 7 ], S33, 0xf6bb4b60L ); /* 39 */
    b = HH( b, c, d, a, x[ 10 ], S34, 0xbebfbc70L ); /* 40 */
    a = HH( a, b, c, d, x[ 13 ], S31, 0x289b7ec6L ); /* 41 */
    d = HH( d, a, b, c, x[ 0 ], S32, 0xeaa127faL ); /* 42 */
    c = HH( c, d, a, b, x[ 3 ], S33, 0xd4ef3085L ); /* 43 */
    b = HH( b, c, d, a, x[ 6 ], S34, 0x4881d05L ); /* 44 */
    a = HH( a, b, c, d, x[ 9 ], S31, 0xd9d4d039L ); /* 45 */
    d = HH( d, a, b, c, x[ 12 ], S32, 0xe6db99e5L ); /* 46 */
    c = HH( c, d, a, b, x[ 15 ], S33, 0x1fa27cf8L ); /* 47 */
    b = HH( b, c, d, a, x[ 2 ], S34, 0xc4ac5665L ); /* 48 */
    /* Round 4 */
    a = II( a, b, c, d, x[ 0 ], S41, 0xf4292244L ); /* 49 */
    d = II( d, a, b, c, x[ 7 ], S42, 0x432aff97L ); /* 50 */
    c = II( c, d, a, b, x[ 14 ], S43, 0xab9423a7L ); /* 51 */
    b = II( b, c, d, a, x[ 5 ], S44, 0xfc93a039L ); /* 52 */
    a = II( a, b, c, d, x[ 12 ], S41, 0x655b59c3L ); /* 53 */
    d = II( d, a, b, c, x[ 3 ], S42, 0x8f0ccc92L ); /* 54 */
    c = II( c, d, a, b, x[ 10 ], S43, 0xffeff47dL ); /* 55 */
    b = II( b, c, d, a, x[ 1 ], S44, 0x85845dd1L ); /* 56 */
    a = II( a, b, c, d, x[ 8 ], S41, 0x6fa87e4fL ); /* 57 */
    d = II( d, a, b, c, x[ 15 ], S42, 0xfe2ce6e0L ); /* 58 */
    c = II( c, d, a, b, x[ 6 ], S43, 0xa3014314L ); /* 59 */
    b = II( b, c, d, a, x[ 13 ], S44, 0x4e0811a1L ); /* 60 */
    a = II( a, b, c, d, x[ 4 ], S41, 0xf7537e82L ); /* 61 */
    d = II( d, a, b, c, x[ 11 ], S42, 0xbd3af235L ); /* 62 */
    c = II( c, d, a, b, x[ 2 ], S43, 0x2ad7d2bbL ); /* 63 */
    b = II( b, c, d, a, x[ 9 ], S44, 0xeb86d391L ); /* 64 */
    state[ 0 ] += a;
    state[ 1 ] += b;
    state[ 2 ] += c;
    state[ 3 ] += d;
    }

    /* Encode把long数组按顺序拆成byte数组�Q�因为java的long�c�d��?4位的�Q�所以只拆低32位，以适应原始c实现的用�?*/
    private void Encode( byte[] output, long[] input, int len)
    {
    int i, j;
    for( i = 0, j = 0; j < len; i ++, j += 4 )
    {
       output[ j ] = ( byte )( input[ i ] & 0xffL );
       output[ j + 1 ] = ( byte )( ( input[ i ] >>> 8 ) & 0xffL );
       output[ j + 2 ] = ( byte )( ( input[ i ] >>> 16 ) & 0xffL );
       output[ j + 3 ] = ( byte )( ( input[ i ] >>> 24 ) & 0xffL );
    }
    }

   /* Decode把byte数组按顺序合成long数组�Q�因为java的long�c�d��?4位的�Q�因此只合成�?2位，�?2位清�?*/
    private void Decode( long[] output, byte[] input, int len )
    {
    int i, j;
    for( i = 0, j = 0; j < len; i ++, j += 4 )
    {
       output[ i ] = b2iu( input[ j ] ) |
        ( b2iu( input[ j + 1 ] ) << 8 ) |
        ( b2iu( input[ j + 2 ] ) << 16 ) |
        ( b2iu( input[ j + 3 ] ) << 24 );
    }
    }

    /* b2iu是一个附加的把byte按照不考虑正负��L(f��ng)��原则�?#8220;升位”函数�Q�因为java没有unsigned�q�算 */
    public static long b2iu( byte b )
    {
    return b < 0 ? b & 0x7F + 128 : b;
    }

    /* byteHEX()用来把一个byte�c�d��的数转换成十六进制的ASCII表示�Q�因为toString�Ҏ(gu��)��无法做到�q�一�?*/
    public static String byteHEX( byte ib )
    {
    char[] Digit = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'D', 'E', 'F' };
    char[] ob = new char[ 2 ];
    ob[ 0 ] = Digit[ ( ib >>> 4 ) & 0x0F ];
    ob[ 1 ] = Digit[ ib & 0x0F ];
    String s = new String( ob );
    return s;
    }

    public static String toMD5( String source )
    {
    MD5 md5 = new MD5();
    return md5.getMD5ofStr( source );
    }
}

可爱的小�?/a> 2009-05-30 01:55 发表评论

��毅收藏�?-----JAVA加密解密工具�c?

Fri, 29 May 2009 17:49:00 GMT

摘要: 在很多的时候，需要将重要信息加密�Q�而以下类��是在java中如何加密和解密�l�常用到的代码：(x��) 1package cn.com.hkgt.apps.util; 2 3 4import java.security.*; 5import... 阅读全文

可爱的小�?/a> 2009-05-30 01:49 发表评论

��毅收藏�?-----从JAR与zip档案文�g中提取Java 资源

Fri, 29 May 2009 16:33:00 GMT

多数 java �E�序员都非常清楚使用 jar 文�g��组�?/span> java 解决�Ҏ(gu��)��的各�U�资源（�?/span> .class 文�g、声韛_��囑փ��Q�打包的优点。刚开始��?/span> jar 文�g的�h帔R��的一个问题是�Q?#8220;如何�?/span> jar 文�g中提取图像呢�Q?#8221;本文��回�{�这个问题，�q�会(x��)提供一个类�Q�这个类使从 jar 文�g中提取�Q何资源变得非常简单！

加蝲 gif 囑փ�
   假定我们有一�?/span> jar 文�g�Q�其中包含我们的应用�E�序要��用的一�l?/span> .gif 囑փ�。下面就是��?/span> JarResources 讉K�� jar 文�g中的囑փ�文�g的方法：(x��)
    JarResources JR=new JarResources(" http://www.bt285.cn /GifBundle.jar");

    Image logo=Toolkit.getDefaultToolkit().createImage(JR.getResources("logo.gif"));

    �q�段代码说明我们可以创徏一�?/span>JarResources对象�Q��ƈ��其初始化�ؓ(f��)包含我们要��用的资源�?/span> jar 文�g -- images.jar。随后我们��?/span>JarResources�?/span>getResource()�Ҏ(gu��)��来�?/span> logo.gif 文�g的原始数据提供给 awt Toolkit �?/span>createImage()�Ҏ(gu��)��?/span>

命名说明
JarResource 是一个非常简单的�C�Z��Q�它说明�?ji��n)如何��?/span> java 所提供的各�U�功能来处理 jar �?/span> zip 档案文�g�?/span>

工作方式
JarReources�cȝ��重要数据域用来跟�t�和存储指定 jar 文�g的内容：(x��)

public final class JarResources {

   public boolean debugon=false;

   private Hashtable htsizes=new Hashtable();
   private Hashtable htjarcontents=new Hashtable();

   private String jarfilename;

�q�样�Q�该�cȝ��实例化设�|?/span> jar 文�g的名�U�ͼ�然后转到init()�Ҏ(gu��)��完成全部实际工作�?/span>

   public JarResources(String jarfilename) {
      this.jarfilename=jarfilename;
      init();
   }

现在�Q?/span>init()�Ҏ(gu��)��只将指定 jar 文�g的整个内容加载到一�?/span> hashtable�Q�通过资源名访问）(j��)中�?/span>

      �q�是一个相当有用的�Ҏ(gu��)��Q�下面我们对它作�q�一步的分析�?/span>ZipFile�c�Mؓ(f��)我们提供�?ji��n)�?/span> jar/zip 档案头信息的基本讉K��Ҏ(gu��)��。这�c�M��于文件系�l�中的目录信息。下面我们列�?/span>ZipFile中的所有条目，�q�用档案中每个资源的大小��d�� htsizes hashtable�Q?/span>

 private void init() {

      try {

          // extracts just sizes only.

          ZipFile zf=new ZipFile(jarFileName);

          Enumeration e=zf.entries();

          while (e.hasMoreElements()) {

              ZipEntry ze=(ZipEntry)e.nextElement();

              if (debugOn) {

                 System.out.println(dumpZipEntry(ze));

              htSizes.put(ze.getName(),new Integer((int)ze.getSize()));

          zf.close();

接下来，我们使用ZipInputStream�c�访问档案�?/span>ZipInputStream�c�d��成了(ji��n)全部��术�Q�允许我们单独读取档案中的每个资源。我们从档案中读取组成每个资源的�_��字节敎ͼ��q�将其存储在 htjarcontents hashtable 中，�(zh��n)�可以通过资源名访问这些数据：(x��)

          // extract resources and put them into the hashtable.

          FileInputStream fis=new FileInputStream(jarFileName);

          BufferedInputStream bis=new BufferedInputStream(fis);

          ZipInputStream zis=new ZipInputStream(bis);

          ZipEntry ze=null;

          while ((ze=zis.getNextEntry())!=null) {

             if (ze.isDirectory()) {

                continue;////啊哟!没有处理子目录中的资源啊 http://www.5a520.cn  ���说520�|?/span>

             if (debugOn) {

                System.out.println(

                   "ze.getName()="+ze.getName()+","+"getSize()="+ze.getSize()

);

             int size=(int)ze.getSize();

             // -1 means unknown size.

             if (size==-1) {

                size=((Integer)htSizes.get(ze.getName())).intValue();

             byte[] b=new byte[(int)size];

             int rb=0;

             int chunk=0;

            while (((int)size - rb) > 0) {

                 chunk=zis.read(b,rb,(int)size - rb);

                 if (chunk==-1) {

                    break;

                 rb+=chunk;

             // add to internal resource hashtable

             htJarContents.put(ze.getName(),b);

             if (debugOn) {

                System.out.println(

                   ze.getName()+" rb="+rb+

                   ",size="+size+

                   ",csize="+ze.getCompressedSize()

);

       } catch (NullPointerException e) {

          System.out.println("done.");

       } catch (FileNotFoundException e) {

          e.printStackTrace();

       } catch (IOException e) {

          e.printStackTrace();

��h��意，用来标识每个资源的名�U�是档案中资源的限定路径名，例如�Q?em>不是包中的类�?/span> -- �?/span> java.util.zip 包中�?/span>ZipEntry�c�d��被命名�ؓ(f��) "java/util/zip/ZipEntry"�Q�而不�?/span> "java.util.zip.ZipEntry"�?/span>

其它�Ҏ(gu��)��:

/**

    * Dumps a zip entry into a string.

    * @param ze a ZipEntry

*/

   private String dumpZipEntry(ZipEntry ze) {

       StringBuffer sb=new StringBuffer();

       if (ze.isDirectory()) {

          sb.append("d ");

       } else {

          sb.append("f ");

       if (ze.getMethod()==ZipEntry.STORED) {

          sb.append("stored   ");

       } else {

          sb.append("defalted ");

       sb.append(ze.getName());

       sb.append("\t");

       sb.append(""+ze.getSize());

       if (ze.getMethod()==ZipEntry.DEFLATED) {

          sb.append("/"+ze.getCompressedSize());

       return (sb.toString());

/**

    * Extracts a jar resource as a blob.

    * @param name a resource name.

*/

   public byte[] getResource(String name) {

      return (byte[])htJarContents.get(name);

代码的最后一个重要部分是��单的��试驱动�E�序。该��试驱动�E�序是一个简单的应用�E�序�Q�它接收 jar/zip 档案名和资源名。它试图发现档案中的资源文�g�Q�然后将成功或失败的消息报告出来�Q?/span>

public static void main(String[] args) throws IOException {

       if (args.length!=2) {

          System.err.println(

             "usage: java JarResources < jar file name> < resource name>"

);

          System.exit(1);

       JarResources jr=new JarResources(args[0]);

       byte[] buff=jr.getResource(args[1]);

       if (buff==null) {

          System.out.println("Could not find "+args[1]+".");

       } else {

          System.out.println("Found "+args[1]+ " (length="+buff.length+").");

}              // End of JarResources class.

�(zh��n)�已�?ji��n)解了(ji��n)这个类。一个易于��用的�c�，它隐藏了(ji��n)使用打包�?/span> jar 文�g中的资源的全部棘手问题�?/span>

��结
如果�(zh��n)�曾�l��(f��)望知道如何从 jar 文�g中提取图像，那么�(zh��n)�现在已学到�?ji��n)一�U�方法。有�?ji��n)本技巧提供的�q�个新类�Q��?zh��n)��׃��仅可以�?/span> jar 文�g处理囑փ��Q�而且可以��提取魔术用�?/span> jar 文�g中的��M��资源�?/span>

可爱的小�?/a> 2009-05-30 00:33 发表评论

��毅收藏�?-----------利用Comparator接口实现�Ҏ(gu��)��List中对象的属性排�?以前��到�q�，没有��q��Q�时间久�?ji��n)忘�(sh��)��(ji��n)。汗�?

Wed, 27 May 2009 08:55:00 GMT

Collections.sort(fileList,   new   FileNodeComparator(form.getSortName(),form.isAsc()));



  class   FileNodeComparator   implements   Comparator{
  private   String   sortName   =   "name";
  private   boolean   isAsc   =   true;
  FileNodeComparator(String   sortName,boolean   isAsc){
  this.sortName   =   sortName;
  this.isAsc   =   isAsc;
  }
  public   int   compare(Object   arg0,   Object   arg1)   {
  。。。。。。。�?nbsp;
  。。。。。。。�?nbsp;
  。。。。。。。�?nbsp;
  。。。。。。。�?nbsp;
  }
  }

可爱的小�?/a> 2009-05-27 16:55 发表评论

��毅收藏�?---------Java反射实现�c�M��与Winform中委托的swing事�g处理

Tue, 26 May 2009 20:02:00 GMT

学习(f��n)�q�Java Swing的程序员?sh��)��定对于Swing中相对较为复杂的事�g驱动模型比较困惑�Q�虽然事仉��动模型在Java Swing中被完完全全的体现出来了(ji��n)�Q�但是对于一个��Y件初学者而言�q�样的近�?#8220;�怽�”的事仉��动模型确实是很难理解的�?/p>

微��Y公司.Net框架与Java Swing的GUI�~�程相比要简单很多，同样是事仉��动模�?Net框架��p��行了(ji��n)大量的封装处理，.Net把这�U�封装称之�ؓ(f��)委托�?Delegate)�Q�其代码如下�Q?

//当btnSubmit按钮被点��M��后要求交�l�btnSubmit_Click�Ҏ(gu��)��处理// EventHandler在中间启到委托器的作用，//它负责将事�g分发到指定的�Ҏ(gu��)��中进行处理this.btnSubmit.Click += new EventHandler(this.btnSubmit_Click);//事�g处理�Ҏ(gu��)��// object sender:事�g源，�q�里指btnSubmit对象// EventArgs e:事�g处理参数�Q�它保存?sh��)��(ji��n)需要提供给�E�序员的必要信息private void btnSubmit_Click(object sender, EventArgs e){　//打印This is a button语句　System.Diagnostics.Debug.WriteLine("This is button");}

作�ؓ(f��)�Ҏ(gu��)��Q�我们来看看Java Swing的事件处理和委托��p��复杂很多代码如下�Q?/p>

            //为btnSubmit增加侦听器SelectHandler�Q�当btnSubmit被点��M���?br />
            //有侦听器的actionPerformed负责处理该点��M��件的业务

            //�׃��事�g源btnSubmit和侦听器�c�SelectHandler处于两个不同的类�?br />
            //��Z��(ji��n)让SelectHandler�c�d��得页面的信息�Q�我们需要将�H�体对象(this)

            //传入��C��听器�?br />
            btnSubmit.addActionListener(new SelectHandler(this));

            //侦听器SelectHandler�Q�它必须实现动作事�gActionListener接口

            //以达��C��件分发的作用

            class SelectHandler implements ActionListener {

            　private CommonDialogDemo form = null;

            　//���窗体对象CommonDialogDemo通过构造函��C��入SelectHandler�c�M��

            　public SelectHandler(CommonDialogDemo form) {

            this.form = form;

            　}

            　//事�g处理�Ҏ(gu��)���Q�当btnSubmit被点击，自动执行以下打印代码

            　publicvoid actionPerformed(ActionEvent e) {

            System.out.println("This is button");

            　}

            }

�Ҏ(gu��)��以上代码�Q�我们可以清晰的看到Java Swing要比.Net的麻�?ch��)的多，而且更不能让人忍受的��是�Q�一个页面如果有多个按钮的话�Q�我们必��针�Ҏ(gu��)��个按钮编写多个事件侦听类�Q�而且�q�些�c�M��般都�?x��)被设��?f��)内部�c�R��学�q��Y件徏模的读者可能知道，内部软�g建模在��Y件工�E�中是不推荐使用的，所以这��L(f��ng)��代码�~�写明显�?x��)增加设计冗余度和复杂度�Q�因此，我们可以考虑自己�~�写一个类��g��.Net中EventHandler一��L(f��ng)��事�g委托�c�L��处理事�g分发�?/p>

�׃��我们无权修改Java的编译器�Q�所以我在这里将�?x��)借助于反��技术，利用一个事件委托类处理所有的点击事�g�Q�代码如下：(x��)

            package cn.softworks.teachersearchsystem.support;
            import java.awt.event.ActionEvent;

            import java.awt.event.ActionListener;

            import java.lang.reflect.Method;
            /**

            *该类是用来处理所有的Swing按钮点击事�g�Q��ƈ�Ҏ(gu��)�����处理权


            *转交�l���用者来处理

            *

            *@authorChen.yu

            *

            */

            publicclass EventHandlerimplements ActionListener {
            　//�l��g所在的�H�体对象

            　private Object form = null;
            　//受到委托的方法名

            　private String methodName = null;
            　/**

            　*构造函�?br />
            　*

            　*@paramform �l��g所在的�H�体对象

            　*@parammethodName 受到委托的方法名

            　*/

            　public EventHandler(Object form,String methodName) {

            this.form = form;

            this.methodName = methodName;

            　}
            　/**

            　*事�g处理委托�Ҏ(gu��)��

            　*/

            　publicvoid actionPerformed(ActionEvent e) {
            //得到�H�体对象的类�?br />
            Class formType = this.form.getClass();
            try {

            　//得到指定委托�Ҏ(gu��)��的类�?

            　Method method = 

            formType.getMethod(this.methodName, new Class[] {e.getClass()});

            　//调用指定的方�?br />
            　method.invoke(this.form, new Object[] {e});
            }catch(Exception ex) {

            　return;

            } 

            　}

            }

现在我们来编写一个测试程序，代码如下�Q?/p>

            btnSearch.addActionListener(new EventHandler(this,"btnSearch_Click"));
            public void btnSearch_Click(ActionEvent e) {

            　System.out.println("This is btnSearch");

            }

从以上代码中我们可以清晰的看刎ͼ�事�g处理和事件委托处于同一�H�体中了(ji��n)�Q?Net方便的Delegate处理被我们用反射实现�?ji��n)�?/p>

可爱的小�?/a> 2009-05-27 04:02 发表评论

��毅收藏�?---------截屏

Thu, 21 May 2009 09:21:00 GMT

通过java.awt.Robot的createScreenCapture截屏.

public static void captureScreen(String fileName) throws Exception {

    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Rectangle screenRectangle = new Rectangle(screenSize);
    Robot robot = new Robot();
    BufferedImage image = robot.createScreenCapture(screenRectangle);
    ImageIO.write(image, "png", new File(fileName));
}

可爱的小�?/a> 2009-05-21 17:21 发表评论

jspmartLoad文�g上传下蝲

Thu, 02 Oct 2008 15:16:00 GMT

此例子是��Z��jspsmartupload�l��g的，jspsmartupload是一个不错的上传下蝲�l��g�Q�但对中文支持不��뀂若下蝲的文件名中有汉字�Q�则��览器在提示另存的文件名�Ӟ��昄��的是一堆�ؕ码，让�h看了(ji��n)很不舒服�Q��ؓ(f��)此，有�h专门修改此组�Ӟ��做了(ji��n)�~�码的�{换工作，��文件名转换为UTF-8形式的编码�Ş式。我用的是网上修改过的，已经可以支持中文�Q�相信你也可以找刎ͼ�如果需要，可以联系我，我会(x��)在第一旉��发给你！

在网上找�?ji��n)很多相兌��料，自己也添加�?ji��n)一些js代码�Q�基本实��C��(ji��n)动态添加删除多文�g上传的功能，如果惌��做得更完��，或者把文�g上传下蝲信息存储到数据库�{�，那就自己��d��善了(ji��n)�Q�以下是所有的源代码：(x��)

(文�g下蝲��Z��安全考虑是按��的方式来进行的�Q�而不是直接给出文件下载�\径地址�Q�所以像�q�雷�{�下载工��h��不能下蝲�?

首先当然是上传下载的��面�?ji��n)，upfile.jsp

<%@ page contentType="text/html;charset=GBK"%>
<html>
<head>
   <title>File Uploadtitle>
<script type="text/javascript">
         function addFile()
        {
            var upFile = '<input type="file" name="file1"><br>';
            document .getElementById ("files").insertAdjacentHTML("beforeEnd",upFile);
        }
        function deleteFile()
        {
            var file = document .getElementById ("files").lastChild;
            if(file == null)
                return;
            document .getElementById ("files").removeChild(file);

            file = document .getElementById ("files").lastChild;   //�U�除换行�W?/span><br>所以要�U�M��?br />             document .getElementById ("files").removeChild(file); //如果在表格里面不�?/span><br>��p��动换行的�Q�可以去掉，自己把握
        }
script>
head>
<body>
<h3>��Z��jspsmart upload�l��g的文件上传下�?/span>h3>
<form action="servlet/ServletUpload" method="post" enctype="multipart/form-data">
   选择文�g�Q?/span><div id="files"><input type="file" name="file1"><br>div>
     <input type="submit" value="上传">
     <input type="button" value="增加文�g" onclick="addFile()">
     <input type="button" value="删除文�g" onclick="deleteFile()">
     <input type="reset" value="重置">
   form>
   <br>
   <form action="servlet/ServletDownload" method="post">
     下蝲文�g的名�U�ͼ�(x��)
     <input type="text" name="downloadFileName" size="20" maxlength="80">
    <input type="submit" value="下蝲">
   form>
body>
html>
然后是实��C��传和下蝲的两个servlet�c?br />
上传文�gServletUpload�c�：(x��)

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;

public class ServletUpload extends HttpServlet {

private ServletConfig config;

public ServletUpload() {
   super();
}

public void destroy() {
   super.destroy(); // Just puts "destroy" string in log
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   int count = 0; //记录文�g上传��M��?br />    SmartUpload mySmartUpload = new SmartUpload();
   mySmartUpload.initialize(config,request, response);
   try {
    //mySmartUpload.setAllowedFilesList("rar,htm,html,jar");//讄��允许上传的文�?br />     mySmartUpload.setDeniedFilesList("exe,jsp,asp");//��止上传的文�?br />     mySmartUpload.setDenyPhysicalPath(true); //拒绝物理路径
    mySmartUpload.setMaxFileSize(5000000);//讄��允许上传文�g最大�ؓ(f��)50000bytes
    mySmartUpload.setTotalMaxFileSize(50000000);//一�ơ上传文件大��最多不��过5000000bytes
    mySmartUpload.upload();
    for(int i=0;i<mySmartUpload.getFiles().getCount();i++){
     com.jspsmart.upload.File myFile = mySmartUpload.getFiles().getFile(i);
     String fileName = myFile.getFileName();
     System.out.println("文�g名：(x��)"+fileName);
    }
    count = mySmartUpload.save("/upload");
    System.out.println(count+"文�g已上�?);
   } catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   doGet(request, response);
}

public void init(ServletConfig config) throws ServletException {
   this.config = config;
}
}

下蝲文�gServletDownload�c�：(x��)

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;

public class ServletDownload extends HttpServlet {

private ServletConfig config;

public ServletDownload() {
   super();
}

public void destroy() {
   super.destroy(); // Just puts "destroy" string in log
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   String temp_fileName = request.getParameter("downloadFileName");
   if(temp_fileName == null || temp_fileName == "")
    return ;
   byte[] temp_t = temp_fileName.getBytes("ISO8859_1");
   String fileName = new String(temp_t, "GBK");
   SmartUpload mySmartUpload = new SmartUpload();
   mySmartUpload.initialize(config, request, response);
   mySmartUpload.setContentDisposition(null);
   /*
   * 原型�Q�public void setContentDisposition(String contentDisposition)
   * 其中�Q�contentDisposition��d��的数据�?br />    * 如果contentDisposition为null�Q�则�l��g��自动添�?attachment;"�Q?br />    * 以表明将下蝲的文件作为附�Ӟ��l�果是IE��览器将�?x��)提�C�另存文�Ӟ��而不是自动打开�q�个文�g
   * �Q�IE��览器一般根据下载的文�g扩展名决定执行什么操作，扩展名�ؓ(f��)doc的将用word�E�序打开�Q?br />    * 扩展名�ؓ(f��)pdf的将用acrobat�E�序打开�Q�等�{�）(j��)�?br />    */
   try {
    mySmartUpload.downloadFile("/upload/"+fileName);

   } catch (SmartUploadException e) {
    e.printStackTrace();
   }
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   doGet(request, response);
}

public void init(ServletConfig config) throws ServletException {
   this.config = config;
}
}

以下是web.xml配置文�g:

="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
    <description>This is the description of my J2EE componentdescription>
    <display-name>This is the display name of my J2EE componentdisplay-name>
    <servlet-name>ServletUploadservlet-name>
    <servlet-class>servlet.ServletUploadservlet-class>
servlet>
<servlet>
    <description>This is the description of my J2EE componentdescription>
    <display-name>This is the display name of my J2EE componentdisplay-name>
    <servlet-name>ServletDownloadservlet-name>
    <servlet-class>servlet.ServletDownloadservlet-class>
servlet>

<servlet-mapping>
    <servlet-name>ServletUploadservlet-name>
    <url-pattern>/servlet/ServletUploadurl-pattern>
servlet-mapping>
<servlet-mapping>
    <servlet-name>ServletDownloadservlet-name>
    <url-pattern>/servlet/ServletDownloadurl-pattern>
servlet-mapping>
<welcome-file-list>
    <welcome-file>index.jspwelcome-file>
welcome-file-list>
web-app>

要实现无��h��上传其实很简单。只要利用iframe卛_��Q�只要把target讄��为隐藏的iframe��就可以�?ji��n)�?br /> �Q�iframe name='hidden_frame' id="hidden_frame" style='display:none'�Q�＜/iframe�Q?/span>

可爱的小�?/a> 2008-10-02 23:16 发表评论

��议泛型

Mon, 22 Sep 2008 11:25:00 GMT

泛型
一、什么是泛型�Q?
通过泛型可以定义�c�d��安全�c�，而不�?x��)损害类型安全、性能或工作效�?

二、实例化泛型
1、可以��用�Q何类型来声明和实例化
2、申明和实例话都必须用一个特定的�c�d��来代替一般类型T
3、例子：(x��)
//原来写法
Public class Stack
{
object[] m_Items;
public void Push(object item)
{...}
public object Pop()
{...}
}
Stack stack = new Stack();
stack.Push(1);
int number = (int)stack.Pop();

//有了(ji��n)泛型�?
Public class Stack
{
T[] m_Items;
public void Push(T item)
{...}
public T Pop()
{...}
}
Stack stack = new Stack ();
stack.Push(1);
int number = (int)stack.Pop();

三：(x��)泛型的好�?
1、一�ơ性的开发、测试和部��v代码�Q�通过��M��c�d��来重用它
2、编译器支持和类型安�?
3、不�?x��)强行对值类型进行装��和取消装箱�Q�或者对引用�c�d��q�行向下强制�c�d��转换�Q�所以性能得到显著提高�?
注：(x��)值类型大概可以提�?00%�Q�引用类型大概�ؓ(f��)100%

四：(x��)多个泛型
1、单个类型可以定义多个泛�?

五：(x��)泛型别名
1、在文�g头部使用using 为特定类型取别名�Q�别名作用范围是整个文�g
2、例�?
using List = LinkedList ;
class ListClient
{
static void Main(string[] args)
{
List list = new List();
list.AddHead(123, "AAA ");
}
}

五：(x��)泛型�U�束
(1)、派生约�?
如：(x��)
public class LinkedList where K:IComparable
{
T Find(K key)
{
if (str.Key.CompareTo(key) == 0)//只有实现�q�个接口才可比较
}
}

注意:
1、所有的�z��U�束必须攑֜��cȝ��实际�z��列表之后
如：(x��)public class LinkedList :IEnumerable where K:IComparable
{...}
2、一个泛型参��C��可以�U�束多个接口�Q�用逗号分隔�Q?
public class LinkedList where K:IComparable ,IConvertible
3、在一个约束中最多只能��用一个基�c?
4、约束的基类不能是密��类或静(r��n)态类
5、不能将System.Delegate或System.Array�U�束为基�c?
6、可以同时约束一个基�c�M��?qi��ng)一个或多个接口�Q�但是该基类必须首先出现在派生约束列表中�?
7、C#允许你将另一个泛型参数指定�ؓ(f��)�U�束
public class MyClass where T:U
{...}
8、可以自己定义基�c�L��接口�q�行泛型�U�束
9、自定义的接口或基类必须与泛型具有一致的可见�?

(2)、构造函数约�?
如：(x��)
class Node where T:new()
{
}
注意�Q?
1、可以将构造函数的�U�束和派生约束结合�v来，前提是构造函数的�U�束出现在约束列表中的最�?

(3)、引�?值类型约�?
1、可以��用struct�U�束��泛型参数约束�ؓ(f��)值类�?如int、bool、enum),或�Q何自定义�l�构
2、同样可以��用class�U�束��泛型参数约束�ؓ(f��)引用�c�d��
3、不能将引用/值类型约束与基类�U�束一起��用，因�ؓ(f��)基类�U�束涉及(qi��ng)到类
4、不能��用结构和默认构造函数约束，因�ؓ(f��)默认构造函数约束也涉及(qi��ng)到类
5、虽然�?zh��n)�可以使用�c�d��默认构造函数约束，但是�q�样做没有�Q何�h(hu��n)�?
6、可以将引用/值类型约束与接口�U�束�l�合��h��Q�前提是引用/值类型约束出现在�U�束列表的开�?

六：(x��)泛型和强制类型�{�?
1、C#�~�译器只允许��泛型参数隐式�{换到Object或约束指定的�c�d��
如：(x��)
interface IS{...}
class BaseClass{...}
class MyClass where T:BaseClass,IS
{
void SomeMethod(T t)
{
IS obj1 = t;
BaseClass obj2 = t;
object obj3 = t;
}
}
2、编译器允许你将泛型参数昄��强制转换到其他�Q何借口�Q�但不能��其转换到类
interface IS{...}
class SomeClass{...}
class MyClass //没有�U�束
{
void SomeMethod(T t)
{
IS obj1 = (IS)t; //可以
SomeClass obj2 = (SomeClass)t //不可�?
}
}
3、可以��用��(f��)时的Object变量�Q�将泛型参数强制转换到其他�Q何类�?
class SomeClass{...}
class MyClass
{
void SomeMethod(T t)
{
object temp = t;
SomeClass obj = (SomeClass)temp;//可以
}
}
注意�Q�这里只是告诉你�q�样写是可以的，但是要不要这样写�Q�不要这样写�Q�因为如果t��实没有�l�承SomeClass�~�译没错但是�q�行��׃��(x��)出错
4、解决上面强制�{换问题，可以使用is和as�q�算�W�进行判�?
public class MyClass
{
public void SomeMethod
{
if (t is int ){...}
if (t is LinkedList ){...}
//如果泛型参数的类型是所查询的类型，则is�q�算�W�返回true
string str = t as string;
//如果�q�写�c�d��兼容�Q�则as��执行强制类型�{换，否则��返回null
if (str != null){...}
LinkedList list = t as LinkedList ;
if (list != null){...}
}
}

七：(x��)�l�承和泛�?
1、在从泛型基�c�L��生，可以提供�c�d��实参�Q�而不是基�c�L��型参�?
public class BaseClass {...}
public class SubClass:BaseClass
2、如果子�c�L��泛型�Q�而非具体的类型实参，则可以��用子�c�L��型参��C��为泛型基�cȝ��指定�c�d��
public class BaseClass {...} public class SubClass :BaseClass {...} 3、在使用子类泛型参数�Ӟ��必须在子�cȝ�别重复在基类�U�别规定的�Q何约�? 4、基�c�d��以定义其�{�֐�使用泛型参数的虚�C�方法，在重写它们时�Q�子�c�d��d��Ҏ(gu��)��{�֐�中提供相应的�c�d��? 如：(x��) public class BaseClass { public virtual T SomeMethod() {...} } public class SubClass:BaseClass { public override int SomeMethod() {...} } 5、如果该子类是泛型，则它�q�可以在重写时��用它自己的泛型参�? public class SubClass :BaseClass { public override T SomeMethod() {...} } 6、你可以定义泛型接口、泛型抽象类�Q�甚��x(ch��ng)��型抽象方法�? 7、不能对泛型参数使用+�?=之类的运��符 public class Calculator { public T Add (T arg1,T arg2) { return arg1 + arg2;//错误 } } 但是我们可以通过泛型抽象�c�R��接口来实现在个功能�Q�因为实现泛型抽象类、接口我们就已经明确传一个参��C��(ji��n)�Q�就可以执行诸如+�q�样的操作�? 八：(x��)泛型�Ҏ(gu��)�� 1、方法可以定义特定于其执行范围的泛型参数 public class MyClass { public void MyMethod (X x) {...} } 2、即使各包含�c�L��本不使用泛型�Q�你也可以定义方法特定的泛型参数 public class MyClass { public void MyMethod (T t) {...} } 注意�Q�该功能只��用于�Ҏ(gu��)��Q�属性，索引器只能��用在�cȝ��作用范围中定义的泛型参数�? 3、调用泛型方�? MyClass obj = new MyClass(); obj.MyMethod (3); 也可以这��P��(x��) MyClass obj = new MyClass(); obj.MyMethod(3); //该功能称为泛型推�? 4、泛型方法也可以有自��q��泛型参数�U�束 pubic class MyClass { public void SomeMethod (T t) where T:IComparable {...} } 5、子�c�L��法实��C��能重复在父��别出现的�U�束 public class BaseClass { public virtual void SomeMethod (T t)where T:new() {...} } pubic class SubClass:BaseClass { public override void SomeMethod (T t)//不能再有�U�束 {...} } 6、静(r��n)态方�? �?r��n)态方法可以定义特定的泛型参数和约�? public class MyClass { public static T SomeMethod (T t,X x) {...} } int number = MyClass .SomeMethod (3, "AAA "); 或者：(x��)int mumber = MyClass .SomeMethod(3, "AAA "); �?ji��)�?x��)泛型委托 1、在某个�c�M��定义的委托可以利用该�cȝ��泛型参数 2、委托�(sh��)��可以定义自己的泛型参�?/strong> 可爱的小�?/a> 2008-09-22 19:25 发表评论

��毅的验证码 Wed, 10 Sep 2008 08:42:00 GMT checkCode.java package com.yz.checkcode; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import com.sun.image.codec.jpeg.JPEGCodec; import com.sun.image.codec.jpeg.JPEGImageEncoder; import java.awt.*; import java.awt.image.*; import java.util.*; public class checkCode extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.reset(); response.setContentType("image/jpeg"); response.setHeader("Pragma","No-cache"); response.setHeader("Cache-Control","no-cache"); response.setHeader("Expires", "Tues, 01 Jan 1980 00:00:00 GMT"); //在内存�(sh��)��创徏图象 int width = 58, height = 18; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); //获取囑�Ş上下�?nbsp; Graphics g = image.getGraphics(); //生成随机�c?nbsp; Random random = new Random(); //讑֮�背景�?nbsp; g.setColor(new Color(201 + random.nextInt(50), 201 + random.nextInt(50), 201 + random.nextInt(50))); g.fillRect(0, 0, width, height); //讑֮�字体 g.setFont(new Font("Times new Roman", Font.PLAIN, 18)); //画边�?nbsp; g.setColor(new Color(255,140,0)); g.drawRect(0,0,width-1,height-1); //随机产生155条干扰线�Q��图象中的认证码不易被其它�E�序探测�?nbsp; g.setColor(new Color(160 + random.nextInt(41), 160 + random.nextInt(41), 160 + random.nextInt(41))); for (int i = 0; i < 155; i++) { int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(12); int yl = random.nextInt(12); g.drawLine(x, y, x + xl, y + yl); } //取随��Z�生的认证�?br /> String src = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKMNOPQRSTUVWXYZ0123456789"; String sRand = ""; for (int i = 0; i < 4; i++) { int position=random.nextInt(src.length()); String radomChar=src.charAt(position)+""; sRand += radomChar; //��认证码昄��到图象中 g.setColor(new Color(20 + random.nextInt(111), 20 + random.nextInt(111), 20 + random.nextInt(111))); //调用函数出来的颜色相同，可能是因为种子太接近�Q�所以只能直接生�?nbsp; g.drawString( radomChar, 13 * i + 6, 16); } //图象生效 g.dispose(); HttpSession session = request.getSession(true); //��认证码存入SESSION session.setAttribute("checkCode", sRand); //输出图象到页�?nbsp; ServletOutputStream out = response.getOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); encoder.encode(image); System.out.println("验证码：(x��)\t"+sRand); out.println(sRand); out.flush(); out.close(); } } getKey.java package com.yz.checkcode; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.ServletInputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class getKey extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); response.setCharacterEncoding("utf-8"); PrintWriter out = response.getWriter(); String key=request.getSession().getAttribute("checkCode").toString(); out.println(key); out.flush(); out.close(); } } 可爱的小�?/a> 2008-09-10 16:42 发表评论 Mon, 25 Aug 2008 04:22:00 GMT 首先我们来看以个��例子：(x��) public class Test { public static void changeStr(String str) { str = "welcome"; } public static void main(String[] args) { String str = "1234"; changeStr(str); System.out.println(str); } } 输出�l�果是什么？wecome?你错�?ji��n)，�?1234 ��Z��么呢�Q�原因如下：(x��) 关于 Java字符串池(String pool) public class Sub{ String str=new String( "good "); //一个地址的传�?new出来的对象，在内存�(sh��)��已经开辟了(ji��n)�I�间 public static void main(String args[]){ Sub ex=new Sub(); ex.change(ex.str); System.out.println(ex.str); } public void change(String bb){ bb= "test ok " } 问题�Q?/font>String str=new String( "good ") 和String str="good"的区别？体会(x��)1�Q?/font>str是一个String�c�d��的对象引用，他是Sub�cȝ��c�d��量。当ex对象引用使用change�Ҏ(gu��)��时。bb是str引用的拷贝。可以通过bb讉K��原str的对象。而方法里当bb="test ok"的时候他把bb指向�?ji��n)一个新的对象中。这时候我们就要引�?nobr oncontextmenu="return false" onmousemove="kwM(0)" id="clickeyekey0" onmouseover="kwE(event,0, this)" style="border-bottom: #6600ff 1px dotted; background-color: transparent; text-decoration: underline" onclick="kwC(event,0)" onmouseout="kwL(event,this)">java字符串的概念�?ji��n)�?/span> 体会(x��)2�Q?/font>字符串池�Q��{�Q?/span>String a = "Hello"; String b = "Hello"; String c = new String("Hello"); String d = new String("Hello"); System.out.println(a == b); System.out.println(b == c); System.out.println(c == d); System.out.println(a.equals(b)); System.out.println(b.equals(c)); System.out.println(c.equals(d)); �l�果是true�Q�false�Q�false�Q�true�Q�true�Q�true。这里就涉及(qi��ng)到字�W�串池�?#8220;字符串池”�Q�是Java��Z��(ji��n)提高内存利用率而采用的措施�Q?/span> 当遇到String a = "Hello"; �q�样的语句时�Q�Java�?x��)先在字�W�串池中��L��是否已经存在"Hello"�q�个字符�?如果没有�Q�则建立字符�?Hello"对象�Q�然后变�?a 指向�q�个地址�Q�然后遇到语句String b = "Hello"�Q�这时字�W�串池中已经�?"Hello"�?ji��n)，所以直接让变量b也指向这个地址�Q�省��M��(ji��n)重新分配的麻�?ch��)。而在Java中，操作�W?#8220;==”对于两个基本型来��_(d��)��是判断其内容是否相同�Q�对于两个对象来��_(d��)��则是判断其地址是否相同�Q�所以a == b�q�回 true�?/span> 那么String c = new String("Hello")又如何处理呢�Q�如果是�q�种写法�Q�则不会(x��)去访问字�W�串池，而是先�ؓ(f��)变量 c 开辟空��_(d��)��然后��值写入空间。所以a == c�q�回false�Q�c == d同样�q�回false�?/span> 至于String的equals�Ҏ(gu��)��Q�因为它比较的不是对象的地址�Q�而是对象的��|��所以都�q�回true��׃��奇怪了(ji��n)�?/span> Java虚拟机有一个字�W�串池，保存着几乎所有的字符串对象。字�W�串表达式��L��指向字符串池中的一个对象。��用new操作创徏的字�W�串对象不指向字�W�串池中的对象但是可以��用intern�Ҏ(gu��)��使其指向字符串池中的对象.�Q�注�Q�如果池中已�l�有相同的字�W�串--使用equals�Ҏ(gu��)��定�Q�则直接�q�回池中的字�W�串�Q�否则先��字�W�串��d��到池中，再返回）(j��)。池中两个相�{�的字符串如果��?#8220;==”来比较将�q�回真�?/span> �ȝ��Q?/font>也就是在change�q�个�Ҏ(gu��)��中，bb已经写入str�I�间。而bb在等�?#8220;test ok”的时候是�q�用字符串池创徏�?ji��n)对象中了(ji��n)。所以不能赋倹{��可以这�?bb="test ok"; this.str=bb; 理解有错误，希望看到的高手可以告诉我�Q�以便我可以更好的修改，谢谢�?ji��n)�?/span> 可爱的小�?/a> 2008-08-25 12:22 发表评论

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