参考资料：
http://www.cnblogs.com/solverpeng/p/5687304.html
视频地址：https://edu.51cto.com/course/1956.html
一、为了更加快捷的开发，为了更少的配置，特别是针对 Web 环境的开发，从 Spring 4.0 之后，Spring 引入了 泛型依赖注入。
二、泛型依赖注入：子类之间的依赖关系由其父类泛型以及父类之间的依赖关系来确定，父类的泛型必须为同一类型。
通俗一点来说：两个子类之间的依赖关系不需要在子类中去声明，而是在父类中进行了声明，而依赖的纽带就是 泛型类型，必须是相同的父类泛型类型才具有依赖关系。
三、UML 类图：
说明：在 BaseService 中通过 @Autowired 注解自动装配了 BaseDao 的实例。而在 UserService 中并没有注入 UserDao 的实例，但是通过父类的泛型类型，
在 UserService 中已经注入了 UserDao 的实例。Department 与之类似。
4：maven项目的例子如下：
pom.xml文件如下：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.yuanqiao</groupId>
<artifactId>JavaWeb</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>JavaWeb Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-core -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>5.1.6.RELEASE</version>
</dependency> <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.1.6.RELEASE</version>
</dependency> <!-- https://mvnrepository.com/artifact/org.springframework/spring-beans -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>5.1.6.RELEASE</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-web -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>5.1.6.RELEASE</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.1.6.RELEASE</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-test -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>5.1.6.RELEASE</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-aop -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>5.1.6.RELEASE</version>
</dependency> <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.11.2</version>
</dependency> <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-api -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.11.2</version>
</dependency> <!-- https://mvnrepository.com/artifact/log4j/log4j -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency> <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.26</version>
</dependency>
<!-- https://mvnrepository.com/artifact/ch.qos.logback/logback-classic -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency> </dependencies>
<build>
<finalName>JavaWeb</finalName>
</build>
</project>
spirng的配置文件annotation-beans.xml的内容如下：
<?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"
xmlns:elasticsearch="http://www.springframework.org/schema/data/elasticsearch"
xsi:schemaLocation="http://www.springframework.org/schema/data/elasticsearch http://www.springframework.org/schema/data/elasticsearch/spring-elasticsearch-1.0.xsd
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"> <!-- 启动spring的注解模式 -->
<context:annotation-config /> <context:component-scan base-package="com.yuanqiao.spring.beans" /> </beans>
package com.yuanqiao.spring.beans;
public class BaseRepository<T> {
public void add(){
System.out.println("如果子类没有重写这个方法，那么会调用父类的该方法，BaseRepository add method...");
}
}
package com.yuanqiao.spring.beans; import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier; public class BaseService<T> { @Autowired
protected BaseRepository<T> baseRepository; public void add() {
System.out.println("打印一下当前baseRepository的类型，看是父类还是子类："+baseRepository);
baseRepository.add();
}
}
package com.yuanqiao.spring.beans;
public class User {
}
package com.yuanqiao.spring.beans; import org.springframework.stereotype.Component; @Component
public class UserRepository extends BaseRepository<User> {
public void add() {
System.out.println("现在调用的是子类的add方法，而不是父类的方法，UserRepository add...");
}
}
package com.yuanqiao.spring.beans; import org.springframework.stereotype.Component; @Component
public class UserService extends BaseService<User> { }
最后测试的main类如下：
package com.yuanqiao.spring.beans; import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; /**
* 泛型依赖注入,可以大大节省开发量
*
* 视频地址：https://edu.51cto.com/course/1956.html
*
*
*
* @author yuanqiao
*
*/
public class Main {
public static void main(String[] args) {
ApplicationContext applicationContext=new ClassPathXmlApplicationContext("annotation-beans.xml"); UserService userService = (UserService)applicationContext.getBean("userService"); userService.add(); UserRepository userRepository = (UserRepository)applicationContext.getBean("userRepository"); userRepository.add(); }
}
输出结果如下：
打印一下当前baseRepository的类型，看是父类还是子类：com.yuanqiao.spring.beans.UserRepository@693fe6c9
现在调用的是子类的add方法，UserRepository add...
现在调用的是子类的add方法，UserRepository add...