Java对象与JSON互相转换jsonlib以及手动创建JSON对象与数组——(二)

　　　　首先声明一下，jsonlib转换与GSON相比太差劲了，操作不是一般的繁琐。GSON可以直接转换成各种集合与对象类型。强烈推荐使用GSON。而且GSON一个方法就可以解决，jsonlib转来转去太繁琐了。

手动创建JSONObject与JSONArray有用，用于读取文件对字符串进行处理

 

-----------------------------jsonlib操作复杂，转换Map与list<map>更是复杂----------------

 

Jar包

User.java

package TestJson_JSONlib;

public class User {

    private String id;
    private String name;
    private Integer age;
    private String address;
    public String getId() {
        return id;
    }
    public int getAge() {
        return age;
    }
    
    public void setAge(Integer age) {
        this.age = age;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public User() {
    }
    public User(String id, String name, Integer age, String address) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.address = address;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", age=" + age + ", address=" + address + "]";
    }
    
    
    
    
}

 

 1.Java对象转json(操作复杂)

对象类型用JSONObject，集合类型用JSONArray。

 

package TestJson_JSONlib;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.xml.bind.UnmarshallerHandler;

import org.junit.Test;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class Bean2JSON {

//    测试单个对象转JSON,转单个对象用JSONObject
    @Test
    public void test1(){
        User user = new User("1", "QIAOZHI",25,"山西太原");
        JSONObject jsonObject =  JSONObject.fromObject(user);
        String json = jsonObject.toString();
        System.out.println(json);   
        //{"id":"1","name":"QIAOZHI","age":25,"address":"山西太原"}
    }
    
    
    
//    测试list转JSON，转集合用JSONArray，会产生[]
    @Test
    public void test2(){
        List<User> list = new ArrayList<User>();
        list.add(new User("1", "QIAOZHI",25,"山西太原"));
        list.add(new User("2", "QIAOZHI",25,"山西太原"));
        list.add(new User("3", "QIAOZHI",25,"山西太原"));
        JSONArray jsonArray =  JSONArray.fromObject(list);
        String json = jsonArray.toString();
        System.out.println(json);
//        [{"id":"1","name":"QIAOZHI","age":25,"address":"山西太原"},{"id":"2","name":"QIAOZHI","age":25,"address":"山西太原"},{"id":"3","name":"QIAOZHI","age":25,"address":"山西太原"}]
    }
    
//    测试map对象转JSON,转单个对象用JSONObject
    @Test
    public void test3(){
        Map<String,User> map = new HashMap<String,User>();
        map.put("1", new User("1", "QIAOZHI",25,"山西太原"));
        map.put("2", new User("2", "QIAOZHI",25,"山西太原"));
        map.put("3", new User("3", "QIAOZHI",25,"山西太原"));
        JSONObject jsonObject=  JSONObject.fromObject(map);
        String json = jsonObject.toString();
        System.out.println(json);
//        {"3":{"address":"山西太原","age":25,"id":"3","name":"QIAOZHI"},"2":{"address":"山西太原","age":25,"id":"2","name":"QIAOZHI"},"1":{"address":"山西太原","age":25,"id":"1","name":"QIAOZHI"}}
    }
    
//    测试list<map>对象转JSON，转集合用JSONArray，会产生[]
    @Test
    public void test4(){
        List<Map<String,User>> list = new ArrayList<>();
        Map<String,User> map1 = new HashMap<String,User>();
        Map<String,User> map2 = new HashMap<String,User>();
        map1.put("map11", new User("1", "QIAOZHI",25,"山西太原"));
        map1.put("map12", new User("2", "QIAOZHI",25,"山西太原"));
        map2.put("21", new User("11", "QIAOZHI",25,"山西太原"));
        map2.put("22", new User("21", "QIAOZHI",25,"山西太原"));
        list.add(map1);
        list.add(map2);
        JSONArray jsonArray =  JSONArray.fromObject(list);
        String json = jsonArray.toString();
        System.out.println(json);
//        [{"map12":{"id":"2","name":"QIAOZHI","age":25,"address":"山西太原"},"map11":{"id":"1","name":"QIAOZHI","age":25,"address":"山西太原"}},{"21":{"id":"11","name":"QIAOZHI","age":25,"address":"山西太原"},"22":{"id":"21","name":"QIAOZHI","age":25,"address":"山西太原"}}]
    }
    
}

 

2.JSON字符串转Java对象与list(只测了转bean与list)

转出来的中间还有空格，使用时候还得去空格。太繁琐了。

在将 Json 形式的字符串转换为 JavaBean 的时候需要注意 JavaBean 中必须有无参构造函数，否则会报找不到初始化方法的错误。

 

package TestJson_JSONlib;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.junit.Test;

import com.google.gson.Gson;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class JSON2Bean {
//    测试json转单个对象
    @Test
    public void test1(){
        String json = "{\"id\":\"1\",\"name\":\"QIAOZHI\",\"age\":25,\"address\":\"山西太原\"}";
        JSONObject jsonObject = JSONObject.fromObject(json);
        System.out.println(jsonObject);  //产生一个json格式的json对象
//        {"id":"1","name":"QIAOZHI","age":25,"address":"山西太原"}
        User user = (User) JSONObject.toBean(jsonObject, User.class);
        System.out.println(user);  
//        User [id=1, name=QIAOZHI, age=null, address=山西太原]
    }
    
    
    
//    测试JSON转list(太反复杂了)
    @SuppressWarnings("unchecked")
    @Test
    public void test2(){
        String json = "[{'id':'1','name':'QIAOZHI','age':25,'address':'山西太原'},{'id':'2','name':'QIAOZHI','age':25,'address':'山西太原'},{'id':'3','name':'QIAOZHI','age':25,'address':'山西太原'}]";
        List<User> list = new ArrayList<User>();
        JSONArray jsonArray = JSONArray.fromObject(json);
        System.out.println(jsonArray);   //产生一个JSON格式的数组
//        [{"id":"1","name":"QIAOZHI","age":25,"address":"山西太原"},{"id":"2","name":"QIAOZHI","age":25,"address":"山西太原"},{"id":"3","name":"QIAOZHI","age":25,"address":"山西太原"}]
        list = (List<User>) JSONArray.toList(jsonArray,User.class);
        System.out.println(list);
//        [User [id=1, name=QIAOZHI, age=null, address=山西太原], User [id=2, name=QIAOZHI, age=null, address=山西太原], User [id=3, name=QIAOZHI, age=null, address=山西太原]]
        System.out.println(list.get(1));
//        User [id=2, name=QIAOZHI, age=null, address=山西太原]
    }
}

 

3.手动创建JSONObject与JSONArray(用于封装JSON转java对象与List集合)

package TestJson_JSONlib;

import org.junit.Test;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class CreateJSONObject {

    @Test
    public void test1(){
//        手动创建一个JSONObject
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("id", "11");
        jsonObject.put("name", "qiaozhi");
        jsonObject.put("age", 30);
        jsonObject.put("address", "山西太原");
        System.out.println(jsonObject);
//        {"id":"11","name":"qiaozhi","age":30,"address":"山西太原"}
        
        JSONObject jsonObject1 = new JSONObject();
        jsonObject1.put("id", "12");
        jsonObject1.put("name", "qiaozhi");
        jsonObject1.put("age", 30);
        jsonObject1.put("address", "山西太原");
        System.out.println(jsonObject1);
//        {"id":"12","name":"qiaozhi","age":30,"address":"山西太原"}
        
        
//        产生一个JSONArray
        JSONArray jsonArray = new JSONArray();
        jsonArray.add(jsonObject);
        jsonArray.add(jsonObject1);
        System.out.println(jsonArray);
//        [{"id":"11","name":"qiaozhi","age":30,"address":"山西太原"},{"id":"12","name":"qiaozhi","age":30,"address":"山西太原"}]
        
        
//        用上述方法转成Java对象与List集合，用于处理数据
    }
}

可用于手动封装JSON对象。

 

补充:JSON字符串转map，与map转json字符串的测试:(其实字符转转map是先转为JSONObject再转为map)

        String accessToken = FetchData.getAccessToken();//{"expires_in":7200,"errmsg":"ok","access_token":"94a50870f92230eb8ad8211b4023675c","errcode":0}
        
        //*******************************json字符串转map
        //转为JSONObject
        JSONObject jsonObject = JSONObject.fromObject(accessToken);
        //转为Map
        Map map = (Map) JSONObject.toBean(jsonObject, Map.class);
        System.out.println(map);
        
        //******************************Map转JSON字符串
        JSONObject jsonStr = JSONObject.fromObject(map);
        System.out.println(jsonStr.toString());

结果:

{expires_in=7200, errmsg=ok, access_token=94a50870f92230eb8ad8211b4023675c, errcode=0}
{"expires_in":7200,"errmsg":"ok","access_token":"94a50870f92230eb8ad8211b4023675c","errcode":0}

 

补充:JSONArray其实是List的子类，转换的时候字符串以[]包裹的可以转为JSONArray，而且要转为JSONArray必须以[    ]开始结束

        String jsonStrs = "[{\"customerId\":19,\"customerName\":\"\tXXX有限公司\"},{\"customerId\":5568,\"customerName\":\"\tXXX展有限公司\"}]";
        // 字符串转为JSONArray，必须以[开始，以]结束
        JSONArray jsonArray = JSONArray.fromObject(jsonStrs);
        System.out.println(jsonArray.size());
        System.out.println(jsonArray.toString());
        System.out.println("=================================================");
        for (int i = 0, length_1 = jsonArray.size(); i < length_1; i++) {
            JSONObject jsonObject = jsonArray.getJSONObject(i);
            System.out.println(jsonObject.toString());
        }

        // jsonArray转list
        System.out.println("=================================================");
        List list = JSONArray.toList(jsonArray);
        System.out.println(list);

结果:

2
[{"customerId":19,"customerName":"\tXXX有限公司"},{"customerId":5568,"customerName":"\tXXX展有限公司"}]
=================================================
{"customerId":19,"customerName":"\tXXX有限公司"}
{"customerId":5568,"customerName":"\tXXX展有限公司"}
=================================================
[net.sf.ezmorph.bean.MorphDynaBean@20c8e08f[
{customerName= XXX有限公司, customerId=19}
], net.sf.ezmorph.bean.MorphDynaBean@640edd19[
{customerName= XXX展有限公司, customerId=5568}
]]

查看JSONArray源码:

 

补充2:其实我们的JSONObject就是Map，我们将字符串转为JSONObject之后数据存入其内置的map中:

        String returnedStr = HttpUtils.doGetWithParams(url, params);//{"errmsg":"ok","department":[{"id":1,"createDeptGroup":true,"name":"开发测试","autoAddUser":true}],"errcode":0}
        // *******************************json字符串转map
        JSONObject jsonObject = JSONObject.fromObject(returnedStr);
        if (jsonObject != null && "ok".equals(jsonObject.get("errmsg"))) {
            return (String) jsonObject.get("department");
        }
        
        return null;

结果:

[{"id":1,"createDeptGroup":true,"name":"开发测试","autoAddUser":true}]

 

查看源码:

   public Object get( Object key ) {
      if( key instanceof String ){
         return get( (String) key );
      }
      return null;
   }

   /**
    * Get the value object associated with a key.
    *
    * @param key A key string.
    * @return The object associated with the key.
    * @throws JSONException if this.isNull() returns true.
    */
   public Object get( String key ) {
      verifyIsNull();
      return this.properties.get( key );
   }

 

　　如果是字符串的话调用字符串调用方法从properties中获取值，properties是什么?应该是个map。。。继续查看源码如下:

   /**
    * The Map where the JSONObject's properties are kept.
    */
   private Map properties;

 

补充2:如果从JSONObject中获取一个不存在的key的时候会报错，而不是返回null，查看源码发现:

   public String getString( String key ) {
      verifyIsNull();
      Object o = get( key );
      if( o != null ){
         return o.toString();
      }
      throw new JSONException( "JSONObject[" + JSONUtils.quote( key ) + "] not found." );
   }

解决办法:先判断一下

                if(jo.containsKey("tel")){
                    userMap.put("officePhone", jo.getString("tel"));
                }

 

 而对于HashMap来说，key不存在是返回null的，源码如下:

    public V get(Object key) {
        if (key == null)
            return getForNullKey();
        Entry<K,V> entry = getEntry(key);

        return null == entry ? null : entry.getValue();
    }

 

总结:

　　1.字符串转JSONArray的时候字符串必须是JSON数组，也就是[{},{},.....];字符串转JSONObject必须是对象,也就是{"key":"value"...},当多个{}{}的时候只会转一个，如下。字符串转JSONArray或者JSONObject调用对应的fromObject(Obj)方法:

        String jsonStrs = "[{\"customerId\":19,\"customerName\":\"\tXXX有限公司\"},{\"customerId\":5568,\"customerName\":\"\tXXX展有限公司\"}]";
        String jsonStrs1 = "{\"customerId\":19,\"customerName\":\"\tXXX有限公司\"},{\"customerId\":5568,\"customerName\":\"\tXXX展有限公司\"}";
        JSONArray fromObject = JSONArray.fromObject(jsonStrs);
        JSONObject fromObject1 = JSONObject.fromObject(jsonStrs1);
        System.out.println(fromObject.toString());
        System.out.println(fromObject1.toString());

结果:

[{"customerId":19,"customerName":"\tXXX有限公司"},{"customerId":5568,"customerName":"\tXXX展有限公司"}]
{"customerId":19,"customerName":"\tXXX有限公司"}

　　2.JSONObject是一个中间对象。如果操作集合调用对应的JSONArray即可。

　　　　字符串转对象可以先调用JSONObject.fromObject(str)转换为JSONObject，然后调用JSONObject.toBean(jsonObject,class)转为对应类型的对象

　　　　对象转JSON字符串可以JSONObject.fromObject(str)转换为JSONObject，然后调用其toString()方法即可。

        Map map = new HashMap<>();
        map.put("x", "x");
        map.put("y", "y");
        // Map转JSON字符串(先为JSONObject)
        JSONObject fromObject = JSONObject.fromObject(map);// 转为JSONObject
        String jsonStr = fromObject.toString();
        System.out.println(jsonStr);
        System.out.println("==========================");
        // JSON转Map字符串(先转为JSONObject)
        JSONObject fromObject2 = JSONObject.fromObject(jsonStr);
        Map bean = (Map) JSONObject.toBean(fromObject2, Map.class);
        System.out.println(bean);

结果:

{"y":"y","x":"x"}
==========================
{y=y, x=x}

 

补充:上面的JSONObject是JSONLib下的类。如果是fastjson包下的JSONObject(alibaba的)使用更简单，字符串转对象与对象转字符串如下:

　　toJSONString(bean)转为JSON串，parseObject(jsonStr,class)转为Bean。

        Map map = new HashMap<>();
        map.put("x", "x");
        map.put("y", "y");
        // bean转JSON字符串
        String jsonString = com.alibaba.fastjson.JSONObject.toJSONString(map);
        System.out.println(jsonString);

        // JSON字符串转bean
        Map parseObject = com.alibaba.fastjson.JSONObject.parseObject(jsonString, Map.class);
        System.out.println(parseObject);

 

 也可以指定指定属性不进行序列化，如下：

        Map<String, String> map = new HashMap<>();
        map.put("x", "x");
        map.put("y", "y");

        // 采用过滤器过滤掉指定属性
        SimplePropertyPreFilter filter = new SimplePropertyPreFilter();
        filter.getExcludes().add("x");
        String jsonString2 = com.alibaba.fastjson.JSONObject.toJSONString(map, filter);
        System.out.println(jsonString2);

结果：

{"y":"y"}