spring 多态 注入

主要内容

spring 多态 注入
利用 PropertySource 实现 多态的动态注入。

更新历史
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环境：spring 4, JDK 1.8； 话不多说，看代码

多态

一个 service 接口， 有若干具体实现

接口 IPolyDiService.java

package com.xxx.service;

public interface IPolyDiService {
    void printName();

}

实现A APolyDiServiceImpl

package com.xxx.service.impl;

import com.xxx.service.IPolyDiService;
import org.springframework.stereotype.Service;

@Service("A_service")
public class APolyDiServiceImpl implements IPolyDiService {

    @Override
    public void printName() {
        System.out.println("This is A PolyDiServiceImpl");
    }
}

实现B BPolyDiServiceImpl

package com.xxx.service.impl;

import com.xxx.service.IPolyDiService;
import org.springframework.stereotype.Service;

@Service("B_service")
public abstract class BPolyDiServiceImpl implements IPolyDiService {
    @Override
    public void printName() {
        System.out.println("This is B PolyDiServiceImpl");
    }
}

动态注入

配置文件 env.properties

可以用其他外置配置替代， 如下， 改变 service 的值， 可以运行时动态注入不同的具体实现。

# service=B
service=A

Junit PolyDiTest

package com.xxx.service;

import com.xxx.service.IPolyDiService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.AnnotationConfigContextLoader;

import javax.annotation.Resource;
import java.text.ParseException;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(loader = AnnotationConfigContextLoader.class)

public class PolyDiTest {

    @Resource(name = "${service}_service")
    private IPolyDiService service;

    @Test
    public void test() throws ParseException {
        service.printName();

    }

    @Configuration
    @PropertySource({ "classpath:conf/env.properties"})
    @ComponentScan(basePackages ={ "com.xxx.service.impl"})
    public static class ContextConfiguration {

    }
}

测试结果

service=A 的结果

This is A PolyDiServiceImpl

service=B 的结果

This is B PolyDiServiceImpl