Jackson 使用 defaultTyping 实现通用的序列化和反序列化

摘要：使用实现通用的序列化和反序列化核心通过方法设置即使使用作为也可以实现相应类型的序列化和反序列化好处只定义一个序列化器就可以了通用引入代码直接使用设置了的直接使用的反序列化，需要给定序列化的类使用设置了的来反序列化，可以使用达到想要的效果

private ObjectMapper createObjectMapping() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
    objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
    return objectMapper;
}

通过 objectMapper.enableDefaultTyping() 方法设置

即使使用 Object.class 作为 jcom.fasterxml.jackson.databind.JavaType 也可以实现相应类型的序列化和反序列化

好处：只定义一个序列化器就可以了（通用）

    com.fasterxml.jackson.core
    jackson-databind
    2.4.1.3


    junit
    junit
    4.12
    test

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.TypeFactory;
import org.junit.Assert;
import org.junit.Test;

import java.io.IOException;
import java.io.Serializable;

/**
 * Created by sealde on 6/7/17.
 */
public class SerializerTest {
    private static final String userString =
            "{"id":null,"username":"admin","password":"admin"}";
    private static final String userStringWithDefaultType =
            "["com.seal_de.domain.UserInfo",{"id":null,"username":"admin","password":"admin"}]";

    /** 直接使用 ObjectMapping  **/
    @Test
    public void serialize() throws JsonProcessingException {
        CustomSerializer serializer = new CustomSerializer(Object.class);
        String s = serializer.serialize(createUser());
        Assert.assertEquals(s, userString);
    }

    /** 设置了 DefaultTyping 的 ObjectMapper **/
    @Test
    public void serializeWithDefaultType() throws JsonProcessingException {
        CustomSerializer serializer = new CustomSerializer(Object.class);
        serializer.setObjectMapper(createObjectMapping());
        String s = serializer.serialize(createUser());
        Assert.assertEquals(s, userStringWithDefaultType);
    }

    /** 直接使用 ObjectMapping 的反序列化，需要给定序列化的类 **/
    @Test
    public void deserialize() throws IOException {
        CustomSerializer serializer = new CustomSerializer(UserInfo.class);
        UserInfo userInfo = serializer.deserialize(userString);
        System.out.println(userInfo);
        Assert.assertEquals(userInfo, createUser());
    }

    /** 使用设置了 DefaultTyping 的 ObjectMapping 来反序列化，可以使用 Object 达到想要的效果 **/
    @Test
    public void deserializeWithDefaultTyping() throws IOException {
        CustomSerializer serializer = new CustomSerializer(Object.class);
        serializer.setObjectMapper(createObjectMapping());
        UserInfo userInfo = (UserInfo) serializer.deserialize(userStringWithDefaultType);
        System.out.println(userInfo);
        Assert.assertEquals(userInfo, createUser());
    }

    private ObjectMapper createObjectMapping() {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        return objectMapper;
    }

    private UserInfo createUser() {
        UserInfo userInfo = new UserInfo();
        userInfo.setUsername("admin");
        userInfo.setPassword("admin");
        return userInfo;
    }

    private class CustomSerializer {
        private final JavaType javaType;
        private ObjectMapper objectMapper = new ObjectMapper();

        public CustomSerializer(JavaType javaType) {
            this.javaType = javaType;
        }

        public CustomSerializer(Class clazz) {
            this.javaType = TypeFactory.defaultInstance().constructType(clazz);
        }

        public void setObjectMapper(ObjectMapper objectMapper) {
            this.objectMapper = objectMapper;
        }

        public String serialize(Object o) throws JsonProcessingException {
            return this.objectMapper.writeValueAsString(o);
        }

        public T deserialize(String s) throws IOException {
            return this.objectMapper.readValue(s, this.javaType);
        }
    }

    private class UserInfo implements Serializable {

        private static final long serialVersionUID = 1L;

        private String id;
        private String username;
        private String password;

        public String getId() {
            return id;
        }

        public void setId(String id) {
            this.id = id;
        }

        public String getUsername() {
            return username;
        }

        public void setUsername(String username) {
            this.username = username;
        }

        public String getPassword() {
            return password;
        }

        public void setPassword(String password) {
            this.password = password;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            UserInfo userInfo = (UserInfo) o;

            if (id != null ? !id.equals(userInfo.id) : userInfo.id != null) return false;
            if (username != null ? !username.equals(userInfo.username) : userInfo.username != null) return false;
            if (password != null ? !password.equals(userInfo.password) : userInfo.password != null) return false;

            return true;
        }

        @Override
        public int hashCode() {
            int result = id != null ? id.hashCode() : 0;
            result = 31 * result + (username != null ? username.hashCode() : 0);
            result = 31 * result + (password != null ? password.hashCode() : 0);
            return result;
        }

        @Override
        public String toString() {
            return "UserInfo{" +
                    "id="" + id + """ +
                    ", username="" + username + """ +
                    ", password="" + password + """ +
                    "}";
        }
    }
}