Spring4.0开始的泛型依赖
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...
