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

核心

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）

maven 引入

        
     
      com.fasterxml.jackson.core
         
     
      jackson-databind
         
     
      2.4.1.3
     
    
        
     
      junit
         
     
      junit
         
     
      4.12
         
     
      test
     
    

代码

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 + '\'' +                    '}';        }    }}