jackson 支援多型資料型別處理，基於此特性我們可以實現靈活強大的型別處理，業務規則處理
同時基於此可以實現動態外掛化的業務處理

參考使用

• 抽象型別定義
  MyUser

 

package com.dalong;

 

import com.fasterxml.jackson.annotation.JsonAutoDetect;

import com.fasterxml.jackson.annotation.JsonTypeInfo;

 

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXTERNAL_PROPERTY, property = "type")
 

@JsonAutoDetect(fieldVisibility= JsonAutoDetect.Visibility.PUBLIC_ONLY, getterVisibility= JsonAutoDetect.Visibility.NONE, isGetterVisibility= JsonAutoDetect.Visibility.NONE, setterVisibility= JsonAutoDetect.Visibility.NONE)

public abstract class MyUser<T> {

    public abstract String printVersion();
 

    public  String getType(){

        return this.getClass().getAnnotation(SourceType.class).value();

    }

    public abstract T instance();

}

SourceType 註解定義

package com.dalong;

 

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;
 

import java.lang.annotation.Target;

 

@Retention(RetentionPolicy.RUNTIME)

@Target({ElementType.TYPE})

public @interface SourceType {

    String value();

    String label() default "";

    String uiConfig() default "";

    boolean configurable() default true;

    boolean listable() default true;

    boolean externalQuerySupported() default false;

}

• 子類
  FirstMyUser

 

package com.dalong;

import java.util.UUID;

@SourceType(value ="FirstMyUser-dalongdemo")

public class FirstMyUser extends MyUser<FirstMyUser> {

    public String name;

    public String classType;

    @Override

    public String printVersion() {

        return UUID.randomUUID().toString();

    }

    @Override

    public FirstMyUser instance() {

        return this;

    }

}

SecondMyUser

package com.dalong;

import java.util.UUID;

@SourceType(value ="SecondMyUser-dalongdemoapp")

public class SecondMyUser extends MyUser<SecondMyUser> {

    public String name;

    public String classType;

 

    @Override

    public String printVersion() {

        return UUID.randomUUID().toString();

    }

 

    @Override

    public SecondMyUser instance() {

        return this;

    }

}

   

• 使用

package com.dalong;

 

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.databind.ObjectMapper;

import com.fasterxml.jackson.databind.jsontype.NamedType;

import java.lang.reflect.InvocationTargetException;

 

public class App {

   static   ObjectMapper objectMapper = new ObjectMapper();

    public static void main(String[] args) throws JsonProcessingException, NoSuchMethodException, InvocationTargetException, IllegalAccessException {

        objectMapper.registerSubtypes(new NamedType(FirstMyUser.class, "dalongdemo"));

        objectMapper.registerSubtypes(new NamedType(SecondMyUser.class, "dalongdemoapp"));

        FirstMyUser bean = new FirstMyUser();

        bean.name="dalong";

        bean.classType="testapp";

        String s = objectMapper.writeValueAsString(bean);

        System.out.println(s);

        SecondMyUser bean2 = new SecondMyUser();

        bean2.name="dalong2";

        bean2.classType="testapp2";

        String s2 = objectMapper.writeValueAsString(bean2);

        System.out.println(s2);

        MyUser myUser=  objectMapper.readValue(s,MyUser.class);

        MyUser myUser2=  objectMapper.readValue(s2,MyUser.class);

        System.out.println(myUser.getType());

        System.out.println(myUser2.getType());

        Object ob= myUser2.instance();

        Object result = ob.getClass().getMethod("getType",null).invoke(ob,null);

        System.out.println(result.toString());

    }

}

• 效果

 

 

說明

整合rest 的玩法，可以基於一個通用的rest 介面定義，基於不同的型別，使用如果類似的方法，同時整合上plugin 處理機制就可以靈活的控制業務資料處理了
參考如下示意整合模式

 

 

參考資料

https://www.baeldung.com/jackson-annotations
https://fasterxml.github.io/jackson-annotations/javadoc/2.4/com/fasterxml/jackson/annotation/JsonTypeInfo.html