Gson-空对象支持

默认情况下，Gson会生成优化后的Json内容，而忽略NULL值。但是GsonBuilder提供了使用GsonBuilder.serializeNulls() 方法在Json输出中显示NULL值的标志。

1 没有使用serializeNulls方法

1.1 编写核心类

MainApp：

package com.yiidian.gson;

import com.google.gson.Gson;

/**
 * 一点教程网 - http://www.yiidian.com
 */
public class MainApp {

    public static void main(String args[]) {

        Gson gson = new Gson();

        Student student = new Student();
        student.setRollNo(1);
        String jsonString = gson.toJson(student);

        System.out.println(jsonString);
        student = gson.fromJson(jsonString, Student.class);
        System.out.println(student);
    }

}

class Student {
    private int rollNo;
    private String name;

    public int getRollNo() {
        return rollNo;
    }

    public void setRollNo(int rollNo) {
        this.rollNo = rollNo;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String toString() {
        return "Student[ name = "+name+", roll no: "+rollNo+ "]";
    }
}

1.2 运行测试

2 使用了serializeNulls方法

2.1 编写核心类

MainApp：

package com.yiidian.gson;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * 一点教程网 - http://www.yiidian.com
 */
public class MainApp {

    public static void main(String args[]) {

        GsonBuilder builder = new GsonBuilder();
        builder.serializeNulls();
        builder.setPrettyPrinting();
        Gson gson = builder.create();

        Student student = new Student();
        student.setRollNo(1);
        String jsonString = gson.toJson(student);

        System.out.println(jsonString);
        student = gson.fromJson(jsonString, Student.class);
        System.out.println(student);
    }

}

class Student {
    private int rollNo;
    private String name;

    public int getRollNo() {
        return rollNo;
    }

    public void setRollNo(int rollNo) {
        this.rollNo = rollNo;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String toString() {
        return "Student[ name = "+name+", roll no: "+rollNo+ "]";
    }
}

2.2 运行测试