Was ist der Unterschied zwischen den Methoden fromJson() und toJson() von Gson in Java?

Gson是一个用于Java的库，可以用来生成JSON。我们可以使用Gson的fromJson()方法将JSON字符串解析为Java对象，并使用Gson的toJson()方法将Java对象转换为JSON字符串。fromJson()方法有两个参数，第一个参数是要解析的JSON字符串，第二个参数是要解析的Java类。我们可以将一个参数传递给toJson()方法，即我们要转换为JSON字符串的Java对象。

fromJson()的语法

public <T> fromJson(java.lang.String json, java.lang.Class<T> classOfT) throws JsonSyntaxException

Example

import com.google.gson.*;
public class FromJsonMethodTest {
   public static void main(String[] args) {
      String jsonString = "{'id':101, 'firstName':'Jai','lastName':'Adithya'}";
      <strong>Gson </strong>gson = new Gson();
      Employee emp = gson.fromJson(jsonString, Employee.class);
      System.out.println(emp);
   }
}
// Employee class<strong>
</strong>class Employee {
   private int id;
   private String firstName;
   private String lastName;
   public Employee() {}
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public String getFirstName() {
      return firstName;
   }
   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }
   public String getLastName() {
      return lastName;
   }
   public void setLastName(String lastName) {
      this.lastName = lastName;
   }
   @Override
   public String toString() {
      StringBuilder sb = new StringBuilder();
      sb.append("Id : " + id);
      sb.append(", FirstName : " + firstName);
      sb.append(", Last Name : " + lastName);
      return sb.toString();
   }
}

输出

Id : 101, FirstName : Jai, Last Name : Adithya<strong>
</strong>

toJson()的语法

public java.lang.String toJson(java.lang.Object src)

Example

import com.google.gson.*;
public class ToJsonMethodTest {
   public static void main(String[] args) {
      Employee emp = new Employee();
      emp.setId(110);
      emp.setFirstName("Raja");
      emp.setLastName("Ramesh");
      Gson gson = new Gson();
      String jsonString = gson.toJson(emp);
      System.out.println(jsonString);
   }
}
// Employee class<strong>
</strong>class Employee {
   private int id;
   private String firstName;
   private String lastName;
   public Employee() {}
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public String getFirstName() {
      return firstName;
   }
   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }
   public String getLastName() {
      return lastName;
   }
   public void setLastName(String lastName) {
      this.lastName = lastName;
   }
}

输出

{"id":110,"firstName":"Raja","lastName":"Ramesh"}

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