Annotation 注解
注入注解：@Autowired 注入
1.加在set方法上， 默认按类型by type，如果在 spring 容器中能够找到多个相同的类型，就从这多个类型找查找有没有一个key的值跟我们的 set 方法的参数名相同，如果有，就注入；没有的话，就无法判断要注入哪一个，导致报错
如果想用byName，使用@Qulifie 需要写在参数上
文件目录
代码：配置文件：beans.xml
<?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.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
<context:component-scan base-package="com.neudeu.service,com.neuedu.dao"></context:component-scan>
</beans>
base-package="com.neudeu.service,com.neuedu.dao 扫描这两个包
Test.java
package com.neuedu.test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test {
public static void main(String[] args) {
ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
}
}
UserDao.java
package com.neuedu.dao;
import org.springframework.stereotype.Component;
@Component //注解方式
//Spring 自动地给这个类创建对象并将这个类放到 String 容器中去
public class UserDao {
public UserDao() {
System.out.println("UserDao...");
}
public void save(){
System.out.println("保存用户信息...");
}
}
@Component //注解方式
UserService.java
package com.neudeu.service;
import org.springframework.stereotype.Component;
import com.neuedu.dao.UserDao;
@Component
public class UserService {
public UserService() {
System.out.println("UserService...");
}
private UserDao userDao;
public void save(){
userDao.save();
}
}
输出：
修改代码：
UserService.java
package com.neudeu.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import com.neuedu.dao.UserDao;
@Component
public class UserService {
public UserService() {
System.out.println("UserService...");
}
private UserDao userDao;
public void save(){
userDao.save();
}
@Autowired //自动的将 userDao的属性注入进来 //修改代码
public void setUserDao(UserDao userDao) { //修改代码
System.out.println("setUserDao..."); //修改代码
this.userDao = userDao; //修改代码
}
}
输出： @Autowired //自动的将 userDao的属性注入进来
修改代码：
Test.java
package com.neuedu.test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.neudeu.service.UserService;
public class Test {
public static void main(String[] args) {
ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
UserService userService = ac.getBean(UserService.class);
userService.save();
}
}
输出：
set 注入 byName，按名称注入
修改代码：配置文件：beans.xml
<?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.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
<context:component-scan base-package="com.neudeu.service,com.neuedu.dao"></context:component-scan>
<bean id="ud" class="com.neuedu.dao.UserDao"></bean>
</beans>
输出：byName，按名称注入
修改代码：beans.xml
<?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.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
<context:component-scan base-package="com.neudeu.service,com.neuedu.dao"></context:component-scan>
<bean id="ud" class="com.neuedu.dao.UserDao"></bean>
<bean id="ud1" class="com.neuedu.dao.UserDao"></bean>
//修改代码
</beans>
UserService.java
package com.neudeu.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
import com.neuedu.dao.UserDao;
@Component
public class UserService {
public UserService() {
System.out.println("UserService...");
}
private UserDao userDao;
public void save(){
userDao.save();
}
@Autowired //自动的将 userDao的属性注入进来
public void setUserDao(@Qualifier("ud1") UserDao userDao) { //修改代码
System.out.println("setUserDao...");
this.userDao = userDao;
}
}
输出：
2.加在属性上，默认按类型bytype； 如果想用byName，使用@Qulifie
修改代码：beans.xml
<?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.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
<context:component-scan base-package="com.neudeu.service,com.neuedu.dao"></context:component-scan>
<bean id="ud" class="com.neuedu.dao.UserDao"></bean>
<bean id="userDao" class="com.neuedu.dao.UserDao"></bean> //修改代码
</beans>
UserService.java
package com.neudeu.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
import com.neuedu.dao.UserDao;
@Component
public class UserService {
@Autowired //自动的将 userDao的属性注入进来
@Qualifier("ud")
private UserDao userDao;
public UserService() {
System.out.println("UserService...");
}
public void save(){
userDao.save();
}
}
输出：
@Resource 注入
默认按名称，名称找不到，按类型；可以指定特定名称
修改代码：
UserService.java
package com.neudeu.service;
import javax.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
import com.neuedu.dao.UserDao;
@Component
public class UserService {
@Resource //修改代码
@Qualifier("ud")
private UserDao userDao;
public UserService() {
System.out.println("UserService...");
}
public void save(){
userDao.save();
}
}
输出：@Resource 作用和 Autowired 一样，不过注入方式不同，前者默认按名称byName，后者默认按类型bytype
强制按名称，找不到则报错
UserService.java
package com.neudeu.service;
import javax.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
import com.neuedu.dao.UserDao;
@Component
public class UserService {
//@Autowired //自动的将 userDao的属性注入进来
@Resource(name="ud1") //修改代码
//@Qualifier("ud")
private UserDao userDao;
public UserService() {
System.out.println("UserService...");
}
public void save(){
userDao.save();
}
}
输出：
组件注解
@Component,@Controller,@Service,@Repository
初始化的名字默认为类名首字母小写，可以指定初始化bean的名字；
实质没有任何区别，功能都一样，在哪个层都可以随意调用，但推荐尽量遵从规范。
