5.Spring MVC 自动装配问题
一.使用@controller注解,实际上也是在IOC容器中配置了,它的id是类的首字母小写
一.使用@controller注解,实际上也是在IOC容器中配置了,它的id是类的首字母小写
1.如果不使用注解,在IOC容器中通过配置来加载bean。
<?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-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"> <!--加载bean--> <bean id="userController" class="com.neuedu.controller.UserController"></bean> </beans>
如果使用注解的方式,在配置文件中要扫描包
<?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-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"> <!-- 扫描包--> <context:component-scan base-package="com.neuedu"></context:component-scan> </beans>
写一个controller层
ackage com.neuedu.controller; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import com.neuedu.service.UserService; @Controllerpublic class UserController { public void sayHello(){ System.out.println("say Hello"); } }
使用@controller注解,实际上也是在IOC容器中配置了,它的id是类的首字母小写
可以写一个Junit test case
public class TestIOC { private ApplicationContext ioc=new ClassPathXmlApplicationContext("applicationContext.xml"); @Test public void test() { //使用UserController类的id来调用 Object bean = ioc.getBean("userController"); System.out.println(bean); } }
@controller也可以更改id,这个注解有一个value属性值
比如:@Controller(value=" zhangsan")
package com.neuedu.controller; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Controller; import com.neuedu.service.UserService; @Controller(vaqlue="zhangsan") public class UserController { public void sayHello(){ System.out.println("say Hello"); } }
在Junit test case中
public class TestIOC { private ApplicationContext ioc=new ClassPathXmlApplicationContext("applicationContext.xml"); @Test public void test() { //使用UserController类的id来调用 Object bean = ioc.getBean("zhangsan"); System.out.println(bean); } }
@Autowired标签
@Controller(value="zhangsan") public class UserController { @Autowired private UserService userService; public void sayHello(){ userService.sayHello(); } }
Autowired标签
1.首先是将使用 UserService 类,
2.如果类有冲突就使用 id,其实就属性名userService
1]首先检测标记了@Autowired注解的属性的类型
[2]根据类型进行装配
[3]如果指定类型的bean不止一个,那么根据需要被装配的属性的属性名做id的值,查找bean
[4]如果根据id值还是没有找到bean,可以使用@Qualifier注解手动指定要装配的bean的id.