spring4.0之六：Generic Qualifier（泛型限定）

旧城等待， 2022-03-30 14:50 153阅读 0赞

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][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：

![285763-20170908142727319-1717379556.png][]

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 ：

Java代码 ![收藏代码][icon_star.png]

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][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。

[http_docs.spring.io_spring_docs_4.0.0.RELEASE_spring-framework-reference_htmlsingle_new-in-4.0]: http://docs.spring.io/spring/docs/4.0.0.RELEASE/spring-framework-reference/htmlsingle/#new-in-4.0
[285763-20170908142727319-1717379556.png]: /images/20220330/9bf81124e4c640988af7a5536fc358fe.png
[icon_star.png]: /images/20220330/0a47920666c345a1943711e6205cb93c.png
[https_github.com_zhangkaitao_es]: https://github.com/zhangkaitao/es