JSON--List集合转换成JSON对象

List
al = articleMng.find(f); System.out.println(al.size()); HttpServletResponse hsr = ServletActionContext.getResponse(); if(null == al){ return ; } for(Article a : al){ System.out.println(a.getId()+a.getDescription()+a.getTitle()); } JSONArray json = new JSONArray(); for(Article a : al){ JSONObject jo = new JSONObject(); jo.put("id", a.getId()); jo.put("title", a.getTitle()); jo.put("desc", a.getDescription()); json.put(jo); } try { System.out.println(json.toString()); hsr.setCharacterEncoding("UTF-8"); hsr.getWriter().write(json.toString()); } catch (IOException e) { e.printStackTrace();

}

上述代码JSONArray是引入的org.json.JSONArray包

而用net.sf.json包下JSONArray的静态方法:fromObject(list) 这是网上大多是都是直接用此方法快捷转换JSON,但是对于Hibernate级联操作关联的对象,这个方法就会报错,如果将映射文件中的级联配置去掉就行了。

另外对于list的要求就是其中的元素是字符串或对象,否则JSON不知道你想要的是什么数据。

<many-to-one name="cmsent" column="comment_tid" class="com.fcms.cms.entity.CmsComment" 
        not-null="false" cascade="delete">

但是级联操作毕竟还是得存在,否则以后数据冗余、多余。

解决方法就是:JSONArray subMsgs = JSONArray.fromObject(object, config);

JsonConfig config = new JsonConfig();
        config.setJsonPropertyFilter(new PropertyFilter() {
            public boolean apply(Object arg0, String arg1, Object arg2) {
                 if (arg1.equals("article") ||arg1.equals("fans")) {
                        return true;
                    } else {
                        return false;
                    }
            }
        });
说明:提供了一个过滤作用,如果遇到关联的对象时他会自动过滤掉,不去执行关联关联所关联的对象。这里我贴出我hibernate中的配置关系映射的代码帮助理解:


        <many-to-one name="article" class="com.fcms.nubb.article" column="article_id"/>
        
        
        <set name="subMessages" table="sub_message" inverse="true" cascade="all" lazy="false" order-by="date asc">
            <key column="theme_id" />
            <one-to-many class="bbs.po.SubMessage" />
        set>

总结:

1. JSONArray subMsgs = JSONArray.fromObject(subMessages, config);其中config是可选的,当出现上面的情况是可以配置config参数,如果没有上面的那种需求就可以直接使用fromObject(obj)方法,它转换出来的就是标准的json对象格式的数据,如下:

{["attr", "content", ...}, ...]}

2. JSONObject jTmsg = JSONObject.fromObject(themeMessage, config);这是专门用来解析标准的pojo,或者map对象的,pojo对象的格式就不用说了,map的形式是这样的{"str", "str"}。

----------------------------------------------------------  分割 -------------------------------------------------------------------------------------------

 对于JSONArray和JSON之前用到想吐了!!!

但是,最近发现个好东西--fastjson (阿里巴巴温少写的一个将Object转为json数据的工具包)

Binary : http://code.alibabatech.com/mvn/releases/com/alibaba/fastjson/1.1.1/fastjson-1.1.1.jar
Source :http://code.alibabatech.com/mvn/releases/com/alibaba/fastjson/1.1.1/fastjson-1.1.1-sources.jar
Subversion : http://code.alibabatech.com/svn/fastjson/

bean

复制代码
package com.nubb.bean;

import java.io.Serializable;

public class Person implements Serializable{
    private static final long serialVersionUID = 1L;
    private String name;
    private int age;
    private String address;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    
    
}
复制代码

 

JsonUtil

复制代码
package com.nubb.test;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.List;

import com.alibaba.fastjson.JSON;
import com.nubb.bean.Person;


public class JSONSerializer {
        private static final String DEFAULT_CHARSET_NAME = "UTF-8";

        public static  String serialize(T object) {
            return JSON.toJSONString(object);
        }

        public static  T deserialize(String string, Class clz) {
            return JSON.parseObject(string, clz);
        }

        public static  T load(Path path, Class clz) throws IOException {
            return deserialize(
                    new String(Files.readAllBytes(path), DEFAULT_CHARSET_NAME), clz);
        }

        public static  void save(Path path, T object) throws IOException {
            if (Files.notExists(path.getParent())) {
                Files.createDirectories(path.getParent());
            }
            Files.write(path,
                    serialize(object).getBytes(DEFAULT_CHARSET_NAME),
                    StandardOpenOption.WRITE,
                    StandardOpenOption.CREATE,
                    StandardOpenOption.TRUNCATE_EXISTING);
        }
        
        public static void main(String[] args) {
            Person person1 = new Person();
            person1.setAddress("address");
            person1.setAge(11);
            person1.setName("amao");
            
            Person person2 = new Person();
            person2.setAddress("address");
            person2.setAge(11);
            person2.setName("amao");
            
            List lp = new ArrayList();
            lp.add(person1);
            lp.add(person2);
            System.out.println(serialize(lp));
        }
        
}
复制代码

输出:

[{"address":"address","age":11,"name":"amao"},{"address":"address","age":11,"name":"amao"}]

 

其中用到的一个jar包可以去下载: http://pan.baidu.com/s/1nCqNV


你可能感兴趣的:(JSON--List集合转换成JSON对象)