Jackson 的基本介绍可以参考 Jackson 使用简介
JsonSerializer 的简单使用
1）实现 JsonSerializer 接口
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import java.io.IOException;
public class ObfuscatedIdSerializer extends JsonSerializer<Integer> {
@Override
public void serialize(Integer value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
if (value == null) {
gen.writeNull();
} else if (value == 1) {
gen.writeString("字符串 1");
} else {
gen.writeNumber(value);
}
}
}
2）定义需要序列化的类
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Person {
private String name;
@JsonSerialize(using = ObfuscatedIdSerializer.class)
private int age;
private int anotherAge;
public static Person from(String name, int age) {
return new Person(name, age, age);
}
}
@JsonSerializer注解的作用是声明使用自定义的序列化类（实现了JsonSerializer接口）。
3）进行序列化操作
public class JacksonDemo1 {
public static void main(String[] args) throws IOException {
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.writeValueAsString(Person.from("zhangsan", 18)));
System.out.println(mapper.writeValueAsString(Person.from("zhangsan", 1)));
}
}
控制台输出：
{"name":"zhangsan","age":18,"anotherAge":18}
{"name":"zhangsan","age":"字符串 1","anotherAge":1}
JsonDeserializer 的简单使用
1）实现 JsonDeserializer 接口
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import java.io.IOException;
public class ObfuscatedIdDeserializer extends JsonDeserializer<Integer> {
@Override
public Integer deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
String obfuscatedId = p.getText().trim();
if (obfuscatedId.isEmpty()) {
return null;
}
if (obfuscatedId.equals("字符串 1")) {
return 1;
}
return Integer.valueOf(obfuscatedId);
}
}
2）定义需要序列化的类
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Person {
private String name;
@JsonSerialize(using = ObfuscatedIdSerializer.class)
@JsonDeserialize(using = ObfuscatedIdDeserializer.class)
private int age;
private int anotherAge;
public static Person from(String name, int age) {
return new Person(name, age, age);
}
}
@JsonDeserialize注解的作用是声明使用自定义的反序列化类（实现了JsonDeserializer接口）。
3）进行序列化操作
public class JacksonDemo2 {
private static ObjectMapper mapper = new ObjectMapper();
public static void main(String[] args) throws IOException {
serializerAndDeserializer(Person.from("zhangsan", 18));
serializerAndDeserializer(Person.from("zhangsan", 1));
}
private static void serializerAndDeserializer(Person person) throws IOException {
String serializer = mapper.writeValueAsString(person);
Person deserializer = mapper.readValue(serializer, Person.class);
System.out.println(serializer);
System.out.println(deserializer);
}
}
控制台输出：
{"name":"zhangsan","age":18,"anotherAge":18}
Person(name=zhangsan, age=18, anotherAge=18)
{"name":"zhangsan","age":"字符串 1","anotherAge":1}
Person(name=zhangsan, age=1, anotherAge=1)
@JacksonAnnotationsInside 的简单使用
@JacksonAnnotationsInside注解的作用是将多个注解组合到一起。
1）定义新的序列化注解
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotationsInside
@JsonSerialize(using = ObfuscatedIdSerializer.class)
public @interface NeedObfuscatedId {
}
2）定义新的反序列化注解
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotationsInside
@JsonDeserialize(using = ObfuscatedIdDeserializer.class)
public @interface NeedUnobfuscatedId {
}
3）在需要序列化的类上使用新的特定注解 @NeedObfuscatedId 和 @NeedUnobfuscatedId，替换之前的 @JsonSerialize 和 @JsonDeserialize 通用注解
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Person {
private String name;
@NeedObfuscatedId
@NeedUnobfuscatedId
private int age;
private int anotherAge;
public static Person from(String name, int age) {
return new Person(name, age, age);
}
}
4）运行上面的 JacksonDemo2，控制台输出和之前一样。
5）把序列化和反序列化注解合并为同一个
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotationsInside
@JsonSerialize(using = ObfuscatedIdSerializer.class)
@JsonDeserialize(using = ObfuscatedIdDeserializer.class)
public @interface ObfuscatedIdSerde {
}
或者
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotationsInside
@NeedObfuscatedId
@NeedUnobfuscatedId
public @interface ObfuscatedIdSerde {
}
6）在需要序列化的类上使用新的注解 ObfuscatedIdSerde 替换上面的 @NeedObfuscatedId 和 @NeedUnobfuscatedId 注解。
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Person {
private String name;
@ObfuscatedIdSerde
private int age;
private int anotherAge;
public static Person from(String name, int age) {
return new Person(name, age, age);
}
}
7）运行上面的 JacksonDemo2，控制台输出和之前一样。
