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Beanutils基本用法

shiwf — Wed, 30 Dec 2009 03:24:00 GMT

Beanutils用了��术般的反射技术，实现了很多夸张有用的功能�Q�都是C/C++时代不敢想的。无��的项目，始终一天都会用得上它。我��是后知后觉了，�W�一回看到它的时候居焉��q��?/span>

1.属性的动态getter,setter

在这框架满天飞的�q�代�Q�不能事事都保证执行getter,setter函数了，有时候属性是要需要根据名字动态取得的�Q�就像这��P��　　

BeanUtils.getProperty(myBean,"code");

而BeanUtils更强的功能是直接讉K��内嵌对象的属性，只要使用点号分隔�?/span>

BeanUtils.getProperty(orderBean, "address.city");

相比之下其他�c�d��的BeanUtils通常都很��单，不能讉K��内嵌的对象，所以经常要用Commons BeanUtils替换它们�?br /> BeanUtils�q�支持List和Map�c�d��的属性。如下面的语法即可取得顾客列表中�W�一个顾客的名字

BeanUtils.getProperty(orderBean, "customers[1].name");

其中BeanUtils会��用ConvertUtils�c�L��字符串�{为Bean属性的真正�c�d��Q�方便从HttpServletRequest�{�对象中提取bean�Q�或者把bean输出到页面�?/span>

而PropertyUtils��׃��原色的保留Bean原来的类型�?/span>

2.beanCompartor 动态排�?

�q�是通过反射�Q�动态设定Bean按照哪个属性来排序�Q�而不再需要在bean的Compare接口�q�行复杂的条件判断�?

List peoples = ...; // Person对象的列表Collections.sort(peoples, new BeanComparator("age"));

如果要支持多个属性的复合排序�Q�如"Order By lastName,firstName"

ArrayList sortFields = new ArrayList();sortFields.add(new BeanComparator("lastName"));

sortFields.add(new BeanComparator("firstName"));

ComparatorChain multiSort = new ComparatorChain(sortFields);

Collections.sort(rows,multiSort);

其中ComparatorChain属于jakata commons-collections包�?br /> 如果age属性不是普通类型，构造函数需要再传入一个comparator对象为age变量排序�?br /> 另外, BeanCompartor本��n的ComparebleComparator, 遇到属性�ؓnull��׃��抛出异常, 也不能设定升序还是降序�?br /> �q�个时候又要借助commons-collections包的ComparatorUtils.

   Comparator mycmp = ComparableComparator.getInstance();
   mycmp = ComparatorUtils.nullLowComparator(mycmp); //允许null
   mycmp = ComparatorUtils.reversedComparator(mycmp); //逆序
   Comparator cmp = new BeanComparator(sortColumn, mycmp);

3.Converter 把Request或ResultSet中的字符串绑定到对象的属�?

�l�常要从request,resultSet�{�对象取出值来赋入bean中，下面的代码谁都写��M��Q�如果不用MVC框架的绑定功能的话�?/span>

   String a = request.getParameter("a");   bean.setA(a);   String b = ....

不妨写一个Binder:

     MyBean bean = ...;    HashMap map = new HashMap();    Enumeration names = request.getParameterNames();    while (names.hasMoreElements())    {      String name = (String) names.nextElement();      map.put(name, request.getParameterValues(name));    }    BeanUtils.populate(bean, map);

其中BeanUtils的populate�Ҏ��或者getProperty,setProperty�Ҏ��其实都会调用convert�q�行转换�?br /> 但Converter只支持一些基本的�c�d��Q�甚臌��java.util.Date�c�d��也不支持。而且它比较笨的一个地�Ҏ��当遇��C��认识的类型时�Q�居然会抛出异常来�?br /> 对于Date�c�d��Q�我参考它的sqldate�c�d��实现了一个Converter,而且��d��了一个设�|�日期格式的函数�?br /> 要把�q�个Converter注册�Q�需要如下语句：

    ConvertUtilsBean convertUtils = new ConvertUtilsBean();

    DateConverter dateConverter = new DateConverter();

    convertUtils.register(dateConverter,Date.class);







//因�ؓ要注册converter,所以不能再使用BeanUtils的静态方法了�Q�必���d��建BeanUtilsBean实例

BeanUtilsBean beanUtils = new BeanUtilsBean(convertUtils,new PropertyUtilsBean());

beanUtils.setProperty(bean, name, value);

4 其他功能

4.1 PropertyUtils�Q�当属性�ؓCollection,Map时的动态读取：

Collection: 提供index

BeanUtils.getIndexedProperty(orderBean,"items",1);
或�?br /> BeanUtils.getIndexedProperty(orderBean,"items[1]");

Map: 提供Key Value
BeanUtils.getMappedProperty(orderBean, "items","111");//key-value goods_no=111
或�?br /> BeanUtils.getMappedProperty(orderBean, "items(111)")

4.2 PropertyUtils�Q�获取属性的Class�c�d��

     public static Class getPropertyType(Object bean, String name)

4.3 ConstructorUtils�Q�动态创建对�?/span>

      public static Object invokeConstructor(Class klass, Object arg)

4.4 MethodUtils�Q�动态调用方�?/span>

    MethodUtils.invokeMethod(bean, methodName, parameter);

4.5 动态Bean �?/span>用DynaBean减除不必要的VO和FormBean

shiwf 2009-12-30 11:24 发表评论

shiwf — Wed, 30 Dec 2009 03:20:00 GMT

1.BeanUtils基本用法�Q?/font>

java 代码

package com.beanutil;
import java.util.Map;
public class User {
private Integer id;
private Map map;
private String username;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Map getMap() {
return map;
}
public void setMap(Map map) {
this.map = map;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
}

java 代码

public class Order {
private User user;
private Integer id;
private String desc;
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}

java 代码

import java.util.HashMap;
import java.util.Map;
import org.apache.commons.beanutils.BeanUtils;
public class Test {
private User user = new User();
private Order order1 = new Order();
private Order order2 = new Order();
private Order order3 = new Order();
private Map map = new HashMap();
private User user1 = new User();
public Test(){
init();
}
public static void main(String[] args) throws Exception{
Test test = new Test();
//输出某个对象的某个属�?
System.out.println(BeanUtils.getProperty(test.user, "username"));
//输出某个对象的内嵌属�?只要使用点号分隔
System.out.println(BeanUtils.getProperty(test.order1, "user.username"));
//BeanUtils�q�支持List和Map�c�d��的属�?对于Map�c�d��Q�则需要以"属性名�Q�key��|��"�?
//对于Indexed�Q�则�?属性名[索引值]"�Q�注意对于ArrayList和数�l�都可以用一��L��方式�q�行操作
System.out.println(BeanUtils.getProperty(test.user1, "map(order2).desc"));
//拯��对象的属性�?
User tempUser = new User();
BeanUtils.copyProperties(tempUser, test.user1);
System.out.println(tempUser.getUsername());
System.out.println(tempUser.getId());
}
//初始�?
public void init(){
user.setId(0);
user.setUsername("zhangshan");
order1.setId(1);
order1.setDesc("order1");
order1.setUser(user);
order2.setId(2);
order2.setDesc("order2");
order2.setUser(user);
order3.setId(3);
order3.setDesc("order3");
order3.setUser(user);
map.put("order1", order1);
map.put("order2", order2);
map.put("order3", order3);
user1.setId(1);
user1.setUsername("lisi");
user1.setMap(map);
}
}

输出�l�果为：

zhangshan
zhangshan
order2
lisi
1

2. BeanCompartor 动态排�?

A:动态设定Bean按照哪个属性来排序�Q�而不再需要再实现bean的Compare接口�q�行复杂的条件判�?/span>

java 代码

//动态设定Bean按照哪个属性来排序�Q�而不再需要再实现bean的Compare接口�q�行复杂的条件判�?
List list = new ArrayList();
list.add(test.order2);
list.add(test.order1);
list.add(test.order3);
//未排序前
for(Order order : list){
System.out.println(order.getId());
}
//排序�?
Collections.sort(list, new BeanComparator("id"));
for(Order order : list){
System.out.println(order.getId());
}

B:支持多个属性的复合排序

java 代码

//支持多个属性的复合排序
List sortFields = new ArrayList();
sortFields.add(new BeanComparator("id"));
sortFields.add(new BeanComparator("desc"));
ComparatorChain multiSort = new ComparatorChain(sortFields);
Collections.sort(list, multiSort);
for(Order order : list){
System.out.println(order.getId());
}

C:使用ComparatorUtils�q�一步指定排序条�?/span>

上面的排序遇到属性�ؓnull��׃��抛出异常, 也不能设定升序还是降序�?br /> 不过�Q�可以借助commons-collections包的ComparatorUtils
BeanComparator�Q�ComparableComparator和ComparatorChain都是实现了Comparator�q�个接口

java 代码

//上面的排序遇到属性�ؓnull��׃��抛出异常, 也不能设定升序还是降序�?
//不过�Q�可以借助commons-collections包的ComparatorUtils
//BeanComparator�Q�ComparableComparator和ComparatorChain都是实现了Comparator�q�个接口
Comparator mycmp = ComparableComparator.getInstance();
mycmp = ComparatorUtils.nullLowComparator(mycmp); //允许null
mycmp = ComparatorUtils.reversedComparator(mycmp); //逆序
Comparator cmp = new BeanComparator("id", mycmp);
Collections.sort(list, cmp);
for(Order order : list){
System.out.println(order.getId());
}

shiwf 2009-12-30 11:20 发表评论