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(转脓)数据库连�?内连接，外连接，交叉�q�接)

AK47 — Wed, 30 Nov 2011 09:24:00 GMT

数据库连接分为：内连接，外连�?左、右�q�接�Q�全�q�接)�Q�交叉连�?br />文章地址 �Q?nbsp;http://www.zxbc.cn/html/20080527/51189.html

转蝲

内连接：把两个表中数据对应的数据查出�?nbsp;

外连接：以某个表为基��把对应数据查出来�Q�全�q�接是以多个表�ؓ基础�Q?nbsp;

student�?nbsp;

no name

1 a

2 b

3 c

4 d

grade�?nbsp;

no grade

1 90

2 98

3 95

内连�?inner join�Q�查找条件中对应的数据，no4没有数据不列出来�Q?nbsp;

语法�Q�select * from student inner join grade on student.no = grade.no

�l�果

student.no name grade.no grade

1 a 1 90

2 b 2 98

3 c 3 95

左连接（左表中所有数据，双��中对应数据）

语法�Q�select * from student left join grade on student.no = grade.no

�l�果�Q?nbsp;

student.no name grade.no grade

1 a 1 90

2 b 2 98

3 c 3 95

4 d

双��接（双��中所有数据，左表中对应数据）

语法�Q�select * from student right join grade on student.no = grade.no

�l�果�Q?nbsp;

student.no name grade.no grade

1 a 1 90

2 b 2 98

3 c 3 95

全连�?nbsp;

语法�Q�select * from student full join grade on student.no = grade.no

�l�果�Q?nbsp;

no name grade

1 a 90

2 b 98

3 c 95

4 d

1 a 90

2 b 98

3 c 95

注：access 中不能直接��用full join �Q�需要��用union all ��左�q�接和右�q�接合�ƈ后才可以

交叉�q�接
��两个表所有行�l�合�Q�连接后的行��Cؓ两个表行数的乘积�Q�笛卡尔�U�）
语法�Q�借用上面的例子应该是

select * from student cross join grade

行数应该�?2�?�Q?br />

no name grade

1 a 90

2 b 98

3 c 95

4 d

1 a 90

2 b 98

3 c 95

4 d

1 a 90

2 b 98

3 c 95

4 d

AK47 2011-11-30 17:24 发表评论

AK47 — Wed, 23 Nov 2011 06:33:00 GMT

JAXB 向Xml非根节点��d��一个或多个属性，直接上代码，关于JAXB的相��x��解可查阅JAVA API�?br />
原创文章�Q��{载请注明出处�?/span>http://www.aygfsteel.com/kangdy/archive/2011/11/23/364635.html

code1: colors�c?nbsp; 根节�?br />

code1

package com.kangdy.test;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "Colors")
@XmlAccessorType(XmlAccessType.FIELD)
public class Colors {

   @XmlElement(name = "red",nillable=true)
   private Red red;

   @XmlElement(name = "blue",nillable=true)
   private Blue blue;

   public Red getRed() {
       return red;
   }

   public Blue getBlue() {
       return blue;
   }

   public void setRed(Red red) {
       this.red = red;
   }

   public void setBlue(Blue blue) {
       this.blue = blue;
   }
}

code2: Red�c?nbsp; 子节�?br />

code2package com.kangdy.test;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "red")
@XmlAccessorType(XmlAccessType.FIELD)
public class Red {

   private String value;

   @XmlAttribute(name = "att1")
   private String att;

   public String getValue() {
       return value;
   }

   public void setValue(String value) {
       this.value = value;
   }

   public String getAtt() {
       return att;
   }

   public void setAtt(String att) {
       this.att = att;
   }

}

code3: �c?Blue 子节�?br />

code3

package com.kangdy.test;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "blue")
@XmlAccessorType(XmlAccessType.FIELD)
public class Blue {
   private String value;

   @XmlAttribute(name = "att2")
   private String att2;

   @XmlAttribute(name = "att1")
   private String att;

   public String getAtt() {
       return att;
   }

   public void setAtt(String att) {
       this.att = att;
   }

   public String getValue() {
       return value;
   }

   public void setValue(String value) {
       this.value = value;
   }

   public String getAtt2() {
       return att2;
   }

   public void setAtt2(String att2) {
       this.att2 = att2;
   }
}

code4: main�c?br />

code4

package com.kangdy.test;

import java.io.StringWriter;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;

public class Jaxbtest {
   public static void main(String[] args) throws Exception {

       StringWriter writer = new StringWriter();
       JAXBContext jc = JAXBContext.newInstance(Colors.class);
       Marshaller ma = jc.createMarshaller();
       ma.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

       Colors colors = new Colors();
       Red red = new Red();
       red.setAtt("att-red");
       red.setValue("red");
       Blue blue = new Blue();
       blue.setValue("blue");
       blue.setAtt("att-blue");
       blue.setAtt2("blue-att2");
       colors.setRed(red);
       colors.setBlue(blue);

       ma.marshal(colors, writer);
       System.out.println(writer.toString());

   }
}

�q�行�l�果�Q?br />

�l�果

        red


        blue

AK47 2011-11-23 14:33 发表评论

(转蝲)关于paramsPrepareParamsStack

AK47 — Wed, 16 Nov 2011 07:39:00 GMT

原帖地址�Q?

http://hi.baidu.com/%CC%AB%C6%BD%D1%F31986/blog/item/110b13b1384e805e08230259.html

转脓

paramsPrepareParamsStack在Struts 2.0中是一个很奇妙的interceptor stack�Q�以至于很多人疑问�ؓ何不��其讄��为默认的interceptor stack。paramsPrepareParamsStack主要解决了ModelDriven和Preparable的配合问题，从字面上理解来说�Q?�q�个stack的拦截器调用的顺序�ؓ�Q�首先params�Q�然后prepare�Q�接下来modelDriven�Q�最后再params。Struts 2.0的设计上要求modelDriven在params之前调用�Q�而业务中prepare要负责准备model�Q�准备model又需要参敎ͼ��q�就需要在 prepare之前�q�行params拦截器设�|�相兛_��敎ͼ��q�个也就是创建paramsPrepareParamsStack的原因�?/span>��程如下�Q?br />    1. params拦截器首先给action中的相关参数赋��|��如id
   2. prepare拦截器执行prepare�Ҏ��Q�prepare�Ҏ��中会�Ҏ��参数�Q�如id�Q�去调用业务逻辑�Q�设�|�model对象
   3. modelDriven拦截器将model对象压入value stack�Q�这里的model对象��是在prepare中创建的
   4. params拦截器再��参数赋值给model对象
   5. action的业务逻辑执行依据此stack�Q�一个action的代码通常如下�Q?

public class UserAction extends ActionSupport implements ModelDriven, Preparable {
   private User user;
   private int id;
   private UserService service; // user business service

   public void setId(int id) {
       this.id = id;
   }

   /**
   * create a new user if none exists, otherwise load the user with the
   * specified id
   */
   public void prepare() throws Exception {
       if (id == 0) {
           user = new User();
       } else {
           user = service.findUserById(id);
       }
   }

   public Object getModel() {
       return user;
   }

   /**
   * create or update the user and then view the created user
   */
   public String update() {
       if (id == 0) {
           service.create(user);
       } else {
           service.update(user);
       }
       return "redirect";
   }

   /**
   * delete the user and go to a default home page
   */
   public String delete() {
       service.deleteById(id);
       return "home";
   }

   /**
   * show the page allowing the user to view the existing data
   */
   public String view() {
       return "view";
   }

   /**
   * show the page allowing the user to view the existing data and change the
   * values
   */
   public String edit() {
       return "input";
   }

在上�q�C��码中�Q�edit和view都不需要根据id再�ؓ界面准备数据�Q�因为prepare�Ҏ��已经准备好了model�Q�这些方法很��单。对于update �Ҏ��Q�prepare首先会从数据库中加蝲数据�Q�然后params拦截器会��参数��g��l�model�Q�在update直接更新��可以，不会出现数据被�ؕ更新的情��c��象Hibernate框架�Q�会判断哪些字段更新了，然后�q�行更新�Q�性能也不会损失�?br /> 通过paramsPrepareParamsStack可以让流�E�更明确�Q�代码更��z�，也更利于大家的交��?/p>

AK47 2011-11-16 15:39 发表评论

(转蝲) Struts 2杂谈�Q?�Q�：ValueStack对象的传送带机制

AK47 — Fri, 11 Nov 2011 09:21:00 GMT

Struts 2杂谈�Q?�Q�：ValueStack对象的传送带�?/strong>�?/div>作者：nokiaguy 原文地址�Q?a >http://blog.csdn.net/nokiaguy/article/details/4684750
转脓
   众所周知�Q�Strut 2的Action�c�通过属性可以获得所有相关的��|��如请求参数、Action配置参数、向其他Action传递属性��|��通过chain�l�果�Q�等�{�。要获得 �q�些参数��|��我们要做的唯一一件事��是在Action�c�M��声明与参数同名的属性，在Struts 2调用Action�cȝ��Action�Ҏ��Q�默认是execute�Ҏ��Q�之前，��׃��为相应的Action属性赋倹{�?br />     要完成这个功能，有很大程度上�Q�Struts 2要依赖于ValueStack对象。这个对象诏�I�整个Action的生命周期（每个Action�cȝ��对象实例会拥有一个ValueStack对象�Q�。当 Struts 2接收��C��?action的请求后�Q�会先徏立Action�cȝ��对象实例�Q��ƈ且将Action�cȝ��对象实例压入ValueStack对象中（实际上，ValueStack对于相当一个栈�Q�，而ValueStack�cȝ��setValue和findValue�Ҏ��可以讄��和获得Action对象的属�?倹{��Struts 2中的某些拦截器正是通过ValueStack�cȝ��setValue�Ҏ��来修改Action�cȝ��属性值的。如params拦截器用于将��h��参数值映��到�?应成Action�cȝ��属性倹{��在params拦截器中在获得请求参数值后�Q�会使用setValue�Ҏ��讄��相应的Action�cȝ��属性�?br />     从这一点可以看出，ValueStack对象��p��一个传送带�Q�当客户端请�?action�Ӟ��Struts 2在创建相应用Action对象后就��Action对象攑ֈ�了ValueStack传送带上，然后ValueStack传送带会带着Action对象�l�过若干拦截器，在每一拦截器中都可以通过ValueStack对象讄��和获得Action对象中的属性倹{��实际上�Q�这些拦截器��q��当于��水�U�作业。如果要�?Action对象�q�行某项加工�Q�再加一个拦截器卛_��Q�当不需要进行这��工作时�Q�直接将该拦截器��L��卛_��?/span>
    下面我们使用一个例子来演示�q�个�q�程。在�q�个例子中实��C��一个拦截器�Q�该拦截器的功能是将一个属性文件中的key-value�Ҏ��成相应的属性的倹{��如下面是一个属性文件的内容�Q?br />
    name = ��h
    price = 10000

    我们可以在Action�c�M��定义name和price属性，在Action中引用这个拦截器后，��׃��自动为属性赋倹{�?br />     在��用该拦截器有如下规则�Q?br />     1. 拦截器读取的属性文件�\径由path参数指定�?br />     2. 属性文件的�~�码格式由encoding参数指定�Q�默认值是UTF-8�?br />     3. 如果某个key中包含有“.”�Q�该�W�号不能出现在标识符中）�Q�则有如下处理方法：
    �Q?�Q�将Action�cȝ��属性名定义为去�?#8220;.”的key。例如，key为person.name�Q�而属性名可定义�ؓpersonname�?br />     �Q?�Q�将Action�cȝ��属性名定义为将“.”替换成其他字�W�的表示�W�号。例如，key为person.name�Q�而属性名可定义�ؓperson_name�Q�其�?#8220;_”由separator参数指定�?br />     4. 如果key太长�Q�也可以直接使用Action参数�q�行映射�Q�例如，key为country.person.name�Q�可做如下映��：
      name
      要注意的是，name属性��g��能包�?#8220;.”�Q�因此，应将key��g��?#8220;.”��L��。现在就可以直接在Action�c�M��定义名�ؓname的属性的�Q�name属性的��g��与key值相同�?br />     5. 上面所有的规则可以同时使用�?br />
拦截器的源代码：

package interceptors;

import java.util.Enumeration;
import java.util.Map;
import java.util.Properties;
import java.io.InputStream;
import java.io.FileInputStream;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.config.entities.ActionConfig;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
import com.opensymphony.xwork2.util.ValueStack;

public class PropertyInterceptor extends AbstractInterceptor
{
    private static final String DEFAULT_PATH_KEY = "path";
    private static final String DEFAULT_ENCODING_KEY = "encoding";
    private static final String DEFAULT_SEPARATOR_KEY = "separator";

    protected String pathKey = DEFAULT_PATH_KEY;
    protected String encodingKey = DEFAULT_ENCODING_KEY;
    protected String separatorKey = DEFAULT_SEPARATOR_KEY;

    public void setPathKey(String pathKey)
    {
        this.pathKey = pathKey;
    }

    public void setEncodingKey(String encodingKey)
    {
        this.encodingKey = encodingKey;
    }

    public void setSeparatorKey(String separatorKey)
    {
        this.separatorKey = separatorKey;
    }

    @Override
    public String intercept(ActionInvocation invocation) throws Exception
    {
        ActionConfig config = invocation.getProxy().getConfig();

        Map<String, String> parameters = config.getParams();
        if (parameters.containsKey(pathKey))
        {
            String path = parameters.get(pathKey);
            String encoding = parameters.get(encodingKey);
            String separator = parameters.get(separatorKey);
            if (encoding == null)
                encoding = "UTF-8";
            if (separator == null)
                separator = "";
            path = invocation.getAction().getClass().getResource(path)
                    .getPath();
            Properties properties = new Properties();
            InputStream is = new FileInputStream(path);
            java.io.Reader reader = new java.io.InputStreamReader(is, encoding);

            properties.load(reader);
            ActionContext ac = invocation.getInvocationContext();
            ValueStack stack = ac.getValueStack();
            System.out.println(stack.hashCode());
            Enumeration names = properties.propertyNames();
            while (names.hasMoreElements())
            {
                //  下面会��用setValue�Ҏ��修改ValueStack对象中的相应属性�?/span>
                String name = names.nextElement().toString();
                if (!name.contains("."))
                    stack.setValue(name, properties.get(name));

                String newName = null;
                newName = parameters.get(name.replaceAll("//.", ""));
                if (newName != null)
                    stack.setValue(newName, properties.get(name));

                if (!separator.equals(""))
                {
                    newName = name.replaceAll("//.", "");
                    stack.setValue(newName, properties.get(name));
                }
                newName = name.replaceAll("//.", separator);
                stack.setValue(newName, properties.get(name));
            }
        }
        return invocation.invoke();
    }
}

用于��试的Action�cȝ��源代码：

package actions;

public class MyAction
{
    private String name;
    private Integer price;
    private String log4jappenderstdout;
    private String log4j_rootLogger;
    private String conversionPattern;

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public Integer getPrice()
    {
        return price;
    }

    public void setPrice(Integer price)
    {
        this.price = price;
    }

    public String getLog4jappenderstdout()
    {
        return log4jappenderstdout;
    }

    public void setLog4jappenderstdout(String log4jappenderstdout)
    {
        this.log4jappenderstdout = log4jappenderstdout;
    }

    public String getLog4j_rootLogger()
    {
        return log4j_rootLogger;
    }

    public void setLog4j_rootLogger(String log4j_rootLogger)
    {
        this.log4j_rootLogger = log4j_rootLogger;
    }

    public String getConversionPattern()
    {
        return conversionPattern;
    }

    public void setConversionPattern(String conversionPattern)
    {
        this.conversionPattern = conversionPattern;
    }

    public String execute()
    {
        System.out.println("name:" + name);
        System.out.println("price:" + price);
        System.out.println("log4jappenderstdout:" + log4jappenderstdout);
        System.out.println("log4j_rootLogger:" + log4j_rootLogger);
        System.out.println("conversionPattern:" + conversionPattern);
        return null;
    }
}

Action�cȝ��配置代码如：

xml version="1.0" encoding="UTF-8" ?>
DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN"
    "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
    <package name="struts" extends="struts-default">

        <interceptors>
            <interceptor name="property"
                class="interceptors.PropertyInterceptor" />
            <interceptor-stack name="myStack">
                <interceptor-ref name="defaultStack" />
                <interceptor-ref name="property" />
            interceptor-stack>
        interceptors>
        <action name="test" class="actions.MyAction">
            <interceptor-ref name="myStack" />
            <param name="path">/log4j.propertiesparam>
            <param name="encoding">UTF-8param>
            <param name="separator">_param>
            <param name="log4jappenderstdoutlayoutConversionPattern">
                conversionPattern
            param>

        action>
    package>
struts>

请将log4j.properties文�g复制到WEB-INF/classes目录�Q��ƈ在该文�g中加入name和price属性�?br />
��试�l�果�Q?br />

name:中国
price:34
log4jappenderstdout:org.apache.log4j.ConsoleAppender
log4j_rootLogger:error, stdout
conversionPattern:%d{ABSOLUTE} %5p %c{1}:%L - %m%n

    �׃��property拦截器在defaultStack后引用，因此�Q�在该拦截器中设�|�的属性值是最�l�结果，如果��property拦截器放�?defaultStack前面�Q�将两个元素掉换一下）�Q�就可以通过同名胜Action配置参数或请求参�?来干预最�l�究输出�l�果了�?

AK47 2011-11-11 17:21 发表评论

AK47 — Fri, 11 Nov 2011 08:19:00 GMT
     摘要: �Q��{�Q�Struts2数据传输的背后机�Ӟ��ValueStack�Q�值栈�Q�原文地址 �Q�http://blog.csdn.net/li_tengfei/article/details/6098134转蝲 1.     数据传输背后机制�Q�ValueStack(值栈) 在这一切的背后�Q�是因�ؓ有了ValueStack�Q�值栈�Q�！ Valu...  阅读全文

AK47 2011-11-11 16:19 发表评论

structs2配置UrlRewriteFilter

AK47 — Wed, 09 Nov 2011 09:22:00 GMT

转蝲每个�|�页或请求都是一个url地址�Q�一般，�q�个地址可能�?do,.page,.action之类的�ƈ加上'?'受��?&'��h��询串�{�构成的一个长长的的url。很urgly�?

一般的url----------------------------------------------------------较好的url
http://www.xxx.net/user/profile.do?id=20001   ====> http://www.xxx.net/user/20001
http://www.xxx.net/forum/board.do?name=java   ====> http://www.xxx.net/forum/java
http://www.xxx.net/forum/thread.do?id=29923   ====> http://www.xxx.net/thread/29923

后者明显较为直观和漂亮�?

使用url rewrite可以很好的改善这个状��c��网站url rewrite应用是非常广泛的�Q�良好的url设计�l�用户带来的非常好的体验�Q�同时也能吸引搜索引擎的注意�?/fieldset>原文地址�Q?a >http://www.iteye.com/topic/53834
使用方式�Q?/strong>
1 配置web.xml文�g
样例�Q?/strong>

       org.springframework.web.context.ContextLoaderListener


       encodingFilter
       org.springframework.web.filter.CharacterEncodingFilter

           encoding
           UTF-8



       encodingFilter
       /*


       osivFilter

           org.springframework.orm.hibernate3.support.OpenSessionInViewFilter



           org.springframework.web.context.request.RequestContextListener


       osivFilter
       /*