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"}