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("[e-mail]"); 
    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", "[e-mail]"); 
    //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", "[e-mail]"); 
    //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":""} 
{"cardlist":[{"cardcode":"888888888","cardname":"bankcard1","cardvalue":99999999},{"cardcode":"999999999","cardname":"bankcard1","cardvalue":222222222}],"sex":"man","age":38,"email":""} 
{"cardlist":[{"cardname":"bankcard1","cardcode":"888888888","cardvalue":99999999},{"cardname":"bankcard2","cardcode":"999999999","cardvalue":222222222}],"sex":"man","age":38,"email":""}