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"}