jakarta.commons包中BeanUtils以及ComparatorUtils的使用

轉自：http://ttitfly.javaeye.com/blog/132900

1.BeanUtils基本用法：

java 代碼

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 代碼

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 代碼

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();
        //輸出某個對象的某個屬性
        System.out.println(BeanUtils.getProperty(test.user, "username"));

        //輸出某個對象的內嵌屬性,只要使用點號分隔
        System.out.println(BeanUtils.getProperty(test.order1, "user.username"));

        //BeanUtils還支持List和Map類型的屬性,對於Map類型，則需要以"屬性名（key值）"的
        //對於Indexed，則爲"屬性名[索引值]"，注意對於ArrayList和數組都可以用一樣的方式進行操作
        System.out.println(BeanUtils.getProperty(test.user1, "map(order2).desc"));

        //拷貝對象的屬性值
        User tempUser = new User();
        BeanUtils.copyProperties(tempUser, test.user1);

        System.out.println(tempUser.getUsername());
        System.out.println(tempUser.getId());




    }

    //初始化
    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);


    }
}

 

輸出結果爲：

zhangshan
zhangshan
order2
lisi
1

 

2. BeanCompartor 動態排序

A:動態設定Bean按照哪個屬性來排序，而不再需要再實現bean的Compare接口進行復雜的條件判斷

java 代碼

//動態設定Bean按照哪個屬性來排序，而不再需要再實現bean的Compare接口進行復雜的條件判斷
        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());
        }
        //排序後
        Collections.sort(list, new BeanComparator("id"));
        for(Order order : list){
            System.out.println(order.getId());
        }

 

B:支持多個屬性的複合排序

java 代碼

//支持多個屬性的複合排序
        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進一步指定排序條件

上面的排序遇到屬性爲null就會拋出異常, 也不能設定升序還是降序。
  不過，可以藉助commons-collections包的ComparatorUtils
  BeanComparator，ComparableComparator和ComparatorChain都是實現了Comparator這個接口

java 代碼

//上面的排序遇到屬性爲null就會拋出異常, 也不能設定升序還是降序。
        //不過，可以藉助commons-collections包的ComparatorUtils
        //BeanComparator，ComparableComparator和ComparatorChain都是實現了Comparator這個接口
        Comparator mycmp = ComparableComparator.getInstance();
        mycmp = ComparatorUtils.nullLowComparator(mycmp);  //允許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());
        }