Java转JSON串的几种方式

昨天在与对端系统调接口的时候，对端系统对我们传过去的json串老是处理不了，后来查原因是应为我们传过去的json串里有json对象数组，因为我们的json串存在表里的，取出来是作为json字符串放到json数组里的，所以带了双引号，对端认为是字符串，不是json对象所以处理不了。

[{"cardName":"bankCard1","cardCode":"888888888","cardValue":99999999},{"cardName":"bankCard2","cardCode":"999999999","cardValue":222222222}] 这种是正确的json对象数组，["{"cardName":"bankCard1","cardCode":"888888888","cardValue":99999999}","{"cardName":"bankCard2","cardCode":"999999999","cardValue":222222222}"]，这种是json字符串数组。

以下总结一下java转JSON串的几种方式：

1、将java对象转成json串
2、通过JSONObject生成json串
3、通过json字符串生成json串

代码通过阿里的fastjson包实现。

代码如下：

1、Person类，包含Crad的List

package com.doit8.test.jsontest.pojo; 
import java.util.ArrayList; 
import java.util.List; 
public class Person { 
  private String username; 
  private String email; 
  private String sex; 
  private int age; 
  private List<Card> cardList=new ArrayList<Card>(); 
  public String getUsername() { 
    return username; 
  } 
  public void setUsername(String username) { 
    this.username = username; 
  } 
  public String getEmail() { 
    return email; 
  } 
  public void setEmail(String email) { 
    this.email = email; 
  } 
  public String getSex() { 
    return sex; 
  } 
  public void setSex(String sex) { 
    this.sex = sex; 
  } 
  public int getAge() { 
    return age; 
  } 
  public void setAge(int age) { 
    this.age = age; 
  } 
  public List<Card> getCardList() { 
    return cardList; 
  } 
  public void setCardList(List<Card> cardList) { 
    this.cardList = cardList; 
  } 
}

2、Card类

package com.doit8.test.jsontest.pojo; 
public class Card { 
  private String cardName; 
  private String cardCode; 
  private Integer cardValue; 
  public String getCardName() { 
    return cardName; 
  } 
  public void setCardName(String cardName) { 
    this.cardName = cardName; 
  } 
  public String getCardCode() { 
    return cardCode; 
  } 
  public void setCardCode(String cardCode) { 
    this.cardCode = cardCode; 
  } 
  public Integer getCardValue() { 
    return cardValue; 
  } 
  public void setCardValue(Integer cardValue) { 
    this.cardValue = cardValue; 
  } 
}

3、JSON处理测试类

package com.doit8.test.jsontest; 
 import java.util.ArrayList; 
import java.util.List; 
import com.alibaba.fastjson.JSON; 
import com.alibaba.fastjson.JSONArray; 
import com.alibaba.fastjson.JSONObject; 
import com.doit8.test.jsontest.pojo.Card; 
import com.doit8.test.jsontest.pojo.Person; 
/** 
* JSON转换 
* 
*/ 
public class App  
{ 
  public static void main( String[] args ) 
  { 
    //1。通过对象生成JSON串，对象里包含对象数组转成JSON串。 
    Person person=new Person(); 
    person.setUsername("xiejava"); 
    person.setSex("man"); 
    person.setAge(38); 
    person.setEmail("xiejava@ishareread.com"); 
    Card card1=new Card(); 
    card1.setCardName("bankCard1"); 
    card1.setCardCode("888888888"); 
    card1.setCardValue(99999999); 
    Card card2=new Card(); 
    card2.setCardName("bankCard1"); 
    card2.setCardCode("999999999"); 
    card2.setCardValue(222222222); 
    //对象数组 
    List<Card> cards=new ArrayList<Card>(); 
    cards.add(card1); 
    cards.add(card2); 
    person.setCardList(cards); 
    String json = JSON.toJSON(person).toString(); 
    System.out.println(json); 
    //2.通过JSON对象生成JSON串 
    JSONObject jObject=new JSONObject(); 
    jObject.put("username", "xiejava"); 
    jObject.put("sex", "man"); 
    jObject.put("age", 38); 
    jObject.put("email", "xiejava@ishareread.com"); 
    //通过JSONArray包装对象数组 
    JSONArray jArray=new JSONArray(); 
    jArray.addAll(cards); 
    jObject.put("cardList", jArray); 
    String json2=jObject.toJSONString(); 
    System.out.println(json2); 
    //3.通过JSON对象生成JSON串 
    JSONObject jObject2=new JSONObject(); 
    jObject2.put("username", "xiejava"); 
    jObject2.put("sex", "man"); 
    jObject2.put("age", 38); 
    jObject2.put("email", "xiejava@ishareread.com"); 
    //构造JSON字符串 
    String cardjsonStr1="{\"cardName\":\"bankCard1\",\"cardCode\":\"888888888\",\"cardValue\":99999999}"; 
    String cardjsonStr2="{\"cardName\":\"bankCard2\",\"cardCode\":\"999999999\",\"cardValue\":222222222}"; 
    JSON.parseObject(cardjsonStr1); 
    JSONArray jArray2=new JSONArray(); 
    //将JSON字符串转成JSON对象，加入到JSONArray，[注意一定要用JSON.parseObject()方法转换成JSON对象，否则还是字符串，转成JSON串的时候会带双引号。] 
    jArray2.add(JSON.parseObject(cardjsonStr1)); 
    jArray2.add(JSON.parseObject(cardjsonStr2)); 
    jObject2.put("cardList", jArray2); 
    String json3=jObject2.toJSONString(); 
    System.out.println(json3); 
  } 
}

pom.xml中引入fastjson包

<dependency> 
  <groupId>com.alibaba</groupId> 
  <artifactId>fastjson</artifactId> 
  <version>1.2.15</version> 
</dependency>

运行结果

{"cardList":[{"cardName":"bankCard1","cardCode":"888888888","cardValue":99999999},{"cardName":"bankCard1","cardCode":"999999999","cardValue":222222222}],"sex":"man","age":38,"email":"xiejava@ishareread.com","username":"xiejava"} 
{"cardList":[{"cardCode":"888888888","cardName":"bankCard1","cardValue":99999999},{"cardCode":"999999999","cardName":"bankCard1","cardValue":222222222}],"sex":"man","age":38,"email":"xiejava@ishareread.com","username":"xiejava"} 
{"cardList":[{"cardName":"bankCard1","cardCode":"888888888","cardValue":99999999},{"cardName":"bankCard2","cardCode":"999999999","cardValue":222222222}],"sex":"man","age":38,"email":"xiejava@ishareread.com","username":"xiejava"}