spring4.0之六：Generic Qualifier（泛型限定）

时间：2021-03-06 21:29:00

Spring 4.0已经发布RELEASE版本，不仅支持Java8，而且向下兼容到JavaSE6/JavaEE6，并移出了相关废弃类，新添加如Java8的支持、Groovy式Bean定义DSL、对核心容器进行增强、对Web框架的增强、Websocket模块的实现、测试的增强等。其中两个我一直想要的增强就是：支持泛型依赖注入、对cglib类代理不再要求必须有空参构造器了。具体更新请参考：

http://docs.spring.io/spring/docs/4.0.0.RELEASE/spring-framework-reference/htmlsingle/#new-in-4.0

model类：

package com.dxz.demo.generic.model;

import java.io.Serializable;

public class Organization implements Serializable {

    private Long id;

    private String name;

}

package com.dxz.demo.generic.model;

import java.io.Serializable;

public class User implements Serializable {

    private Long id;

    private String name;

    public User(Long id, String name) {

        this.id = id;

        this.name = name;

    }

}

dao类：

package com.dxz.demo.generic.dao;

import java.io.Serializable;

public abstract class BaseDao<M extends Serializable> {

    public void save(M m) {

        System.out.println("BaseDao save:" + m);

    }

}

package com.dxz.demo.generic.dao;

import org.springframework.stereotype.Repository;

import com.dxz.demo.generic.model.Organization;

@Repository

public class OrganizationDao extends BaseDao<Organization> {

}

package com.dxz.demo.generic.dao;

import org.springframework.stereotype.Repository;

import com.dxz.demo.generic.model.User;

@Repository

public class UserDao extends BaseDao<User> {

}

以前Service写法：

package com.dxz.demo.generic.service.old;

import java.io.Serializable;

import com.dxz.demo.generic.dao.BaseDao;

public abstract class BaseService<M extends Serializable> {

    private BaseDao<M> dao;

    public void setDao(BaseDao<M> repository) {

        this.dao = repository;

    }

    public void save(M m) {

        System.out.println("old-----");

        dao.save(m);

    }

}

package com.dxz.demo.generic.service.old;

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

import org.springframework.stereotype.Service;

import com.dxz.demo.generic.dao.OrganizationDao;

import com.dxz.demo.generic.model.Organization;

@Service

public class OrganizationService extends BaseService<Organization> {

    @Autowired

    public void setOrganizationRepository(OrganizationDao organizationDao) {

        setDao(organizationDao);

    }

}

package com.dxz.demo.generic.service.old;

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

import org.springframework.stereotype.Service;

import com.dxz.demo.generic.dao.UserDao;

import com.dxz.demo.generic.model.User;

@Service

public class UserService extends BaseService<User> {

    @Autowired

    public void setUserDao(UserDao userDao) {

        setDao(userDao);

    }

}

可以看到，以前必须再写一个setter方法，然后指定注入的具体类型，然后进行注入；

service泛型Service的写法

package com.dxz.demo.generic.service.newf;

import java.io.Serializable;

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

import com.dxz.demo.generic.dao.BaseDao;

public abstract class BaseService<M extends Serializable> {

    @Autowired

    protected BaseDao<M> dao;

    public void save(M m) {

        System.out.println("newf ----");

        dao.save(m);

    }

}

package com.dxz.demo.generic.service.newf;

import org.springframework.stereotype.Service;

import com.dxz.demo.generic.model.Organization;

@Service

public class GOrganizationService extends BaseService<Organization> {

}

package com.dxz.demo.generic.service.newf;

import org.springframework.stereotype.Service;

import com.dxz.demo.generic.model.User;

@Service("gUserService")

public class GUserService extends BaseService<User> {

}

spring对bean的装配类：

package com.dxz.demo.generic;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

@Configuration

//添加自动扫描注解，basePackages为待注册bean的包路径

@ComponentScan(basePackages = "com.dxz.demo.generic")

public class GenericDemoConfiguration {

    public GenericDemoConfiguration() {

        System.out.println("GenericDemoConfiguration容器启动初始化。。。");

    }

}

package com.dxz.demo.generic;

import org.springframework.context.annotation.Configuration;

import org.springframework.context.annotation.Import;

@Configuration

@Import(GenericDemoConfiguration.class)

public class GenericDemoConfig {

}

测试类：

package com.dxz.demo.generic;

import org.springframework.context.ApplicationContext;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.dxz.demo.generic.model.User;

public class TestMain {

    public static void main(String[] args) {

        // @Configuration注解的spring容器加载方式，用AnnotationConfigApplicationContext替换ClassPathXmlApplicationContext

        ApplicationContext context = new AnnotationConfigApplicationContext(GenericDemoConfig.class);

        com.dxz.demo.generic.service.newf.BaseService service = (com.dxz.demo.generic.service.newf.BaseService)context.getBean("gUserService");

        service.save(new User(1L,"duan"));

        com.dxz.demo.generic.service.old.BaseService service2 = (com.dxz.demo.generic.service.old.BaseService)context.getBean("userService");

        service2.save(new User(1L,"duan"));

    }

}

大家可以看到，现在的写法非常简洁。支持泛型式依赖注入。

结果：

spring4.0之六：Generic Qualifier（泛型限定）

这个也是我之前非常想要的一个功能，这样对于那些基本的CRUD式代码，可以简化更多的代码。

如果大家用过Spring data jpa的话，以后注入的话也可以使用泛型限定式依赖注入 ：

  1. @Autowired
  2. private Repository<User> userRepository;

对于泛型依赖注入，最好使用setter注入，这样万一子类想变，比较容易切换。比如https://github.com/zhangkaitao/es，如果有多个实现时，子类可以使用@Qualifier指定使用哪一个。

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