基于JAVA中的四种JSON解析方式详解

public class Student {

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

public class Grade {

  private int id;
  private String name;
  private ArrayList<Student> stus;
  public Grade(int id, String name, ArrayList<Student> stus) {
    super();
    this.id = id;
    this.name = name;
    this.stus = stus;
  }
  public Grade() {
    super();
  }
  @Override
  public String toString() {
    return "Grade [id=" + id + ", name=" + name + ", stus=" + stus + "]";
  }
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public ArrayList<Student> getStus() {
    return stus;
  }
  public void setStus(ArrayList<Student> stus) {
    this.stus = stus;
  }

}

public class JSONTest {

  //解析JSON
  @Test
  public void test1() throws JSONException{
    //对象嵌套数组嵌套对象
    String json1="{'id':1,'name':'JAVAEE-1703','stus':[{'id':101,'name':'刘一','age':16}]}";
    //数组
    String json2="['北京','天津','杭州']";

    //1、
    //解析第一层---对象
    JSONObject jObject1=new JSONObject(json1);
    Grade grade=new Grade();
    grade.setId(jObject1.getInt("id"));
    grade.setName(jObject1.getString("name"));
    ArrayList<Student> stus=new ArrayList<>();
    grade.setStus(stus);
    //解析第二层----数组
    JSONArray jsonArray2=jObject1.getJSONArray("stus");
    //遍历数组获取元素----对象
    for(int i=0;i<jsonArray2.length();i++){
      //解析第三层----对象
      JSONObject jObject3=jsonArray2.getJSONObject(i);
      Student student=new Student(jObject3.getInt("id"), jObject3.getString("name"), jObject3.getInt("age"));
      grade.getStus().add(student);
    }

    System.out.println(grade);

    //获取当前对象的所有属性的迭代器对象
//   Iterator<String> iterator=jObject1.keys();
//   while (iterator.hasNext()) {
//     String key = iterator.next();
//     System.out.println("属性："+key);
//   }

    //2、
    //获取数组对象
    JSONArray jArray=new JSONArray(json2);
    ArrayList<String> list=new ArrayList<>();
    //遍历获取元素
    for(int i=0;i<jArray.length();i++){
      //jArray.optString(i);//等价于getXXX
      list.add(jArray.getString(i));
    }
    System.out.println("解析结果："+list);
  }
  //生成JSON
  @Test
  public void test2() throws JSONException{
    JSONObject jo1=new JSONObject();
    jo1.put("id", 1001);
    jo1.put("name", "范老");
    jo1.put("age", 20);
    JSONObject jo2=new JSONObject();
    jo2.put("id", 1002);
    jo2.put("name", "平平");
    jo2.put("age", 19);
    JSONArray ja2=new JSONArray();
    ja2.put(jo1);
    ja2.put(jo2);
    JSONObject jo3=new JSONObject();
    jo3.put("id", 11);
    jo3.put("name", "JAVAEE-1704");
    jo3.put("stus",ja2);    
    String json=jo3.toString();
    System.out.println(json);

  }

}

public class GSONTest {

  //解析
  @Test
  public void test1() {
    // 对象嵌套数组嵌套对象
    String json1 = "{'id':1,'name':'JAVAEE-1703','stus':[{'id':101,'name':'刘一','age':16}]}";
    // 数组
    String json2 = "['北京','天津','杭州']";

    Gson gson=new Gson();
    //1、
    //解析对象：第一个参数：待解析的字符串 第二个参数结果数据类型的Class对象
    Grade grade=gson.fromJson(json1, Grade.class);
    System.out.println(grade);

    //2、
    //解析数组要求使用Type
    ArrayList<String> list=gson.fromJson(json2, 
        new TypeToken<ArrayList<String>>(){}.getType());
    System.out.println(list);
  }
  //生成
  @Test
  public void test2(){
    ArrayList<Student> list=new ArrayList<>();
    for(int i=1;i<3;i++){
      list.add(new Student(101+i, "码子", 20+i));
    }
    Grade grade=new Grade(100001,"张三", list);
    Gson gson=new Gson();
    //将对象转换为诶JSON格式字符串
    String json=gson.toJson(grade);
    System.out.println(json);

  }
}

public class FASTJson {

  //解析
  @Test
  public void test1() {
    // 对象嵌套数组嵌套对象
    String json1 = "{'id':1,'name':'JAVAEE-1703','stus':[{'id':101,'name':'刘铭','age':16}]}";
    // 数组
    String json2 = "['北京','天津','杭州']";
    //1、
    //静态方法
    Grade grade=JSON.parseObject(json1, Grade.class);
    System.out.println(grade);
    //2、
    List<String> list=JSON.parseArray(json2, String.class);
    System.out.println(list);
  }
  //生成
  @Test
  public void test2(){
    ArrayList<Student> list=new ArrayList<>();
    for(int i=1;i<3;i++){
      list.add(new Student(101+i, "码子", 20+i));
    }
    Grade grade=new Grade(100001,"张三", list);
    String json=JSON.toJSONString(grade);
    System.out.println(json);
  }
}

public class JackSonTest {

  //解析
  @Test
  public void test1() throws Exception{
    // 对象嵌套数组嵌套对象
    String json1 = "{\"id\":1,\"name\":\"JAVAEE-1703\",\"stus\":[{\"id\":101,\"name\":\"刘一\",\"age\":16}]}";
    // 数组
    String json2 = "[\"北京\",\"天津\",\"杭州\"]";
    //1、
    ObjectMapper mapper=new ObjectMapper();
    Grade grade=mapper.readValue(json1, Grade.class);
    System.out.println(grade);
    //2、
    ArrayList<String> list=mapper.readValue(json2, 
        new TypeReference<ArrayList<String>>() {
    });
    System.out.println(list);

  }
  //生成
  @Test
  public void test2() throws JsonProcessingException{
    ArrayList<Student> list=new ArrayList<>();
    for(int i=1;i<3;i++){
      list.add(new Student(101+i, "码子", 20+i));
    }
    Grade grade=new Grade(100001,"张三", list);
    ObjectMapper mapper=new ObjectMapper();
    //将对象转换为JSON格式字符串
    String json=mapper.writeValueAsString(grade);
    System.out.println(json);
  }
}