安卓開發之Gson實作序列化與反序列化

文章預覽

• 前言
• 操作
• • 1、導入依賴
  • 2、JavaBean
  • • 2.1、user.java
    • 2.2、Job.java
  • 3、對Java對象進行序列化與反序列化
  • 4、對Aarray、List進行序列化與反序列化
  • 5、對Map、Set集合進行序列化與反序列化
• 注解解釋

前言

GSON彌補了JSON的許多不足的地方，在實際應用中更加适用于Java開發。在這裡，我們主要講解的是利用GSON來操作java對象和json資料之間的互相轉換，包括了常見的對象序列化和反序列化的知識。

參考文章

https://www.jianshu.com/p/75a50aa0cad1

https://www.yiibai.com/gson/gson_overview.html

操作

1、導入依賴

2、JavaBean

2.1、user.java

package com.enjoy.gsondemo.bean;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class User {
    @Expose
    private String userName;
    @Expose
    private String password;
    @Expose
    private int age;
    @Expose
    private boolean isStudent;


    @Expose
    private Job job;


    //serialize：是否參與序列化，deserialize是否參與反序列化
    @Expose(serialize = false, deserialize = false)
    private int test1;

    private transient int test2;

    @Expose
    //無法以class作為字段名
    @SerializedName("class")
    private int cls;


    public User(String userName, String password, int age, boolean isStudent) {
        this.userName = userName;
        this.password = password;
        this.age = age;
        this.isStudent = isStudent;
    }

    public void setTest1(int test1) {
        this.test1 = test1;
    }

    public void setTest2(int test2) {
        this.test2 = test2;
    }

    public void setCls(int cls) {
        this.cls = cls;
    }

    public String getUserName() {
        return userName;
    }

    public String getPassword() {
        return password;
    }

    public int getAge() {
        return age;
    }

    public boolean isStudent() {
        return isStudent;
    }

    public Job getJob() {
        return job;
    }

    public void setJob(Job job) {
        this.job = job;
    }

    @Override
    public String toString() {
        return "User{" +
                "userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                ", isStudent=" + isStudent +
                ", job=" + job +
                ", test1=" + test1 +
                ", test2=" + test2 +
                ", cls=" + cls +
                '}';
    }
}

           

2.2、Job.java

package com.enjoy.gsondemo.bean;

public class Job {
    private String name;
    private int salary;

    public Job(String name, int salary) {
        this.name = name;
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "Job{" +
                "name='" + name + '\'' +
                ", salary=" + salary +
                '}';
    }
}

           

3、對Java對象進行序列化與反序列化

@Test
    public void testNestedObject() {
        //java對象
        User u1 = new User("zzuli", "123", 18, false);
        Job job = new Job("勞工", 10000);
        u1.setJob(job);
        //Gson提供的Gson對象
        Gson gson = new Gson();
        //序列化
        String json = gson.toJson(u1);
        System.out.println("序列化：" + json);

        User u2 = gson.fromJson(json, User.class);
        System.out.println("反序列化:" + u2.getUserName() + "-" + u2.getPassword() +"-"+u2.getJob());
    }
           

4、對Aarray、List進行序列化與反序列化

package com.enjoy.gsondemo;

import com.enjoy.gsondemo.bean.User;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import org.junit.Test;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;

public class ArrayUnitTest {
    @Test
    public void testArray() {
        User[] users1 = new User[3];
        //java對象
        users1[0] = new User("Lance", "123", 18, false);
        users1[1] = new User("Alex", "123", 88, true);
        //Gson提供的Gson對象
        Gson gson = new Gson();
        //序列化
        String json = gson.toJson(users1);
        System.out.println("序列化:"+json);

        User[] users2 = gson.fromJson(json, User[].class);
        System.out.println("反序列化0:"+users2[0]);
        System.out.println("反序列化1:"+users2[1]);
        System.out.println("反序列化2:"+users2[2]);

    }

    @Test
    public void testListObject() {
        List<User> list1 = new ArrayList<>();
        list1.add(new User("Lance", "123", 18, false));
        list1.add(new User("Alex", "123", 88, true));
        list1.add(null);
        //Gson提供的Gson對象
        Gson gson = new Gson();
        //序列化
        String json = gson.toJson(list1);
        System.out.println("序列化:"+json);

        //反序列化
        Type type = new TypeToken<List<User>>() {
        }.getType();
        List<User> list2 = gson.fromJson(json, type);
        System.out.println("反序列化0:"+list2.get(0).getUserName());
        System.out.println("反序列化1:"+list2.get(1));
        System.out.println("反序列化2:"+list2.get(2));
    }
}

           

Array

List

5、對Map、Set集合進行序列化與反序列化

package com.enjoy.gsondemo;

import com.enjoy.gsondemo.bean.User;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import org.junit.Test;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class MapUnitTest {
    @Test
    public void testMap() {
        Map<String, User> map1 = new HashMap<>();
        //java對象
        map1.put("1", new User("Lance", "123", 18, false));
        map1.put("2", new User("Alex", "123", 88, true));
        map1.put("3", null);
        map1.put(null, null);
        //Gson提供的Gson對象
        Gson gson = new Gson();
        //序列化
        String json = gson.toJson(map1);
        System.out.println(json);

        Type type = new TypeToken<Map<String, User>>() {
        }.getType();
        Map<String, User> map2 = gson.fromJson(json, type);
        System.out.println(map2.get(null));
        System.out.println(map2.get("1"));
    }

    @Test
    public void testSet() {
        Set<User> set1 = new HashSet<>();
        set1.add(new User("Lance", "123", 18, false));
        set1.add(new User("Alex", "123", 88, true));
        set1.add(null);
        //Gson提供的Gson對象
        Gson gson = new Gson();
        //序列化
        String json = gson.toJson(set1);
        System.out.println(json);

        //反序列化
        Type type = new TypeToken<Set<User>>() {
        }.getType();
        Set<User> set2 = gson.fromJson(json, type);
        Iterator<User> iterator = set2.iterator();
        while (iterator.hasNext()) {
            User next = iterator.next();
            System.out.println("反序列化：" + next);
        }

    }
}

           

Map

Set

注解解釋

@SerializedName

注解

用于手動指定序列化的key值

@SerializedName("money")
private String salary;

@SerializedName({"money", "salary"})  // 可以有多個備選值
private String salary;
           

@Expose()

注解

果想要讓java類的某些字段不參加序列化或反序列化，可以顯示來設定。如：

@Expose(serialize=false,deserialize=false)
private String name;
           

注意使用該注解進行序列化與反序列化需要一些列方式建立Gson對象

//Gson提供的Gson對象
  Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();