Gson在Java中的fromJson()和toJson()方法之間的差異是什麼？

Gson是一個用於Java的函式庫，可以用來產生JSON。我們可以使用Gson的fromJson()方法將JSON字串解析為Java對象，並使用Gson的toJson()方法將Java對象轉換為JSON字串。 fromJson()方法有兩個參數，第一個參數是要解析的JSON字串，第二個參數是要解析的Java類別。我們可以將一個參數傳遞給toJson()方法，也就是我們要轉換為JSON字串的Java物件。

fromJson()的語法

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();
   }
}

輸出

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

toJson()的語法

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;
   }
}

輸出

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

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