Spring 架構泛型注入（4.x新特性）

今天看一下Spring的泛型注入。4.x可以為子類注入子類對應的泛型類型的成員變量的類型。

以前Service寫法

BaseService.java

package com.spring.test.generic.di.old;

public class BaseService<T> {
    protected BaseRepository<T> repository;

    public void setRepository(BaseRepository<T> repository) {
        this.repository = repository;
    }

    public void add() {
        System.out.println("add...");
        System.out.println(repository);
    }
}
           

BaseRepository.java

package com.spring.test.generic.di.old;

public class BaseRepository<T> {
}
           

UserService.java

package com.spring.test.generic.di.old;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService extends BaseService<User> {
    @Autowired  
    public void setUserRepository(UserRepository userRepository) {  
        setRepository(userRepository);  
    }  
}
           

UserRepository.java

package com.spring.test.generic.di.old;

import org.springframework.stereotype.Repository;

@Repository
public class UserRepository extends BaseRepository<User> {
}
           

User.java

package com.spring.test.generic.di.old;

public class User {
}
           

可以看出以前的泛型注入需要使用setter方法。

Spring 4.x注入例子

BaseService.java

package com.spring.test.generic.di;

import org.springframework.beans.factory.annotation.Autowired;

public class BaseService<T> {

    @Autowired
    protected BaseRepository<T> repository;

    public void add() {
        System.out.println("add...");
        System.out.println(repository);
    }
}
           

BaseRepository.java

package com.spring.test.generic.di;

public class BaseRepository<T> {
}
           

UserService.java

package com.spring.test.generic.di;

import org.springframework.stereotype.Service;

@Service
public class UserService extends BaseService<User> {
    //不需要添加setter方法，spring會根據該類的泛型User擷取對應Repository
}
           

UserRepository.java

package com.spring.test.generic.di;

import org.springframework.stereotype.Repository;

@Repository
public class UserRepository extends BaseRepository<User> {
}
           

User.java

package com.spring.test.generic.di;

public class User {
}
           

Main.java

package com.spring.test.generic.di;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-generic-di.xml");
        UserService userService = (UserService) ctx.getBean("userService");
        userService.add();
    }
}
           

beans-generic-di.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="com.spring.test.generic.di"></context:component-scan>
</beans>