之前使用的是fastjson，感觉gson不错，抽空学了下！！

依赖

Gradle:

dependencies {
  implementation 'com.google.code.gson:gson:2.8.6'
}

Maven:

<dependency>
  <groupId>com.google.code.gson</groupId>
  <artifactId>gson</artifactId>
  <version>2.8.6</version>
</dependency>

github地址 :https://github.com/google/gson

序列化与反序列化

对象序列化

/**
     * @author lsc
     * <p>对象序列化 </p>
     */
    @Test
    public void test1(){
        User user = new User();
        user.setId("a1");
        user.setName("zszxz");
        user.setAge("16");
        Gson gson = new Gson();
        String userJson = gson.toJson(user);
        // {"id":"a1","name":"zszxz","age":"16"}
        System.out.println(userJson);
    }

结论；将对象转为json字符串；

对象反序列化

    /**
     * @author lsc
     * <p>对象反序列化 </p>
     */
    @Test
    public void test2(){
        String userStr =  "{\"id\":\"a1\",\"name\":\"zszxz\",\"age\":\"16\"}";
        Gson gson = new Gson();
        User user = gson.fromJson(userStr, User.class);
        // User(id=a1, name=zszxz, age=16)
        System.out.println(user);
    }

结论：将json字符串转为对象；

数组序列化

   /**
     * @author lsc
     * <p>数组反序列 </p>
     */
    @Test
    public void test3(){
        String arrayStr = "[\"a\", \"b\", \"c\"]";
        Gson gson = new Gson();
        String[] abc = gson.fromJson(arrayStr, String[].class);
        Arrays.stream(abc).forEach(e -> {
            System.out.println(e);
        });
    }

输出

a
b
c

结论: 字符串数组转为数组对象；

数组反序列化

    /**
     * @author lsc
     * <p>数组反序列 </p>
     */
    @Test
    public void test4(){
        Gson gson = new Gson();
        String[] abc = {"a","b","c"};
        String json = gson.toJson(abc);
        // ["a","b","c"]
        System.out.println(json);
    }

结论：将字符串数组转为数组字符串；

TypeAdapter

将 json对象转为对象

@Test
    public void test8() throws IOException {
        Gson gson = new Gson();
        TypeAdapter<User> typeAdapter = gson.getAdapter(User.class);
        String jsonStr =  "{\"id\":\"a1\",\"name\":\"zszxz\",\"age\":\"16\"}";
        User user = typeAdapter.fromJson(jsonStr);
        //User(id=a1, name=null, age=16)
        System.out.println(user);
    }

将对象序列化为对象字符串；

@Test
    public void test9() throws IOException {
        Gson gson = new Gson();
        TypeAdapter<User> typeAdapter = gson.getAdapter(User.class);
        User user = new User();
        user.setId("a1");
        user.setName("zszxz");
        user.setAge("16");
        String userStr = typeAdapter.toJson(user);
        //{"id":"a1","username":"zszxz","age":"16"}
        System.out.println(userStr);
    }

常用注解

@SerializedName 修改序列化名称；

User对象将 name 序列名称为 username;

/**
 * @author lsc
 * <p> </p>
 */
@Data
public class User {

    private String id;

    @SerializedName("username")
    private String name;

    private String age;
}

测试代码

/**
     * @author lsc
     * <p>对象序列化 </p>
     */
    @Test
    public void test1(){
        User user = new User();
        user.setId("a1");
        user.setName("zszxz");
        user.setAge("16");
        Gson gson = new Gson();
        String userJson = gson.toJson(user);
        // {"id":"a1","username":"zszxz","age":"16"}
        System.out.println(userJson);
    }

结论：输出的字符串,name 字段变为 username;

@Expose()注解

@Expose()注解默认参与序列化和反序列化
@Expose(serialize = false, deserialize = false) 不参与序列化，也不参与反序列化
@Expose(serialize = false) 只参与反序列化
@Expose(deserialize = false) 只参与序列化

Json对象与Json数组

构建json对象

	@Test
    public void test5(){
        JsonObject jsonObject = new JsonObject();
        jsonObject.addProperty("name","知识追寻者");
        jsonObject.addProperty("age",18);
        // 构建json对象{"name":"知识追寻者","age":18}
        System.out.println("构建json对象" + jsonObject);
    }

构建json数组

    @Test
    public void test6() {
        JsonArray jsonArray = new JsonArray();
        jsonArray.add("a");
        jsonArray.add("b");
        jsonArray.add("c");
        jsonArray.add("d");
        // 构建json数组["a","b","c","d"]
        System.out.println("构建json数组" + jsonArray);
    }

Json对象中加入json数组

	@Test
    public void test7() {
        // json对象
        JsonObject jsonObject = new JsonObject();
        jsonObject.addProperty("name","知识追寻者");
        jsonObject.addProperty("age",18);
        // json数组
        JsonArray jsonArray = new JsonArray();
        jsonArray.add("a");
        jsonArray.add("b");
        jsonArray.add("c");
        jsonArray.add("d");
        // json对象中加入json数组
        jsonObject.add("abcd",jsonArray);
        System.out.println(jsonObject);
    }

输出

{"name":"知识追寻者","age":18,"abcd":["a","b","c","d"]}

gson使用总结

依赖