Spring Bean装载 Spring Bean装载方式代码实例解析
WODioe 人气:0这篇文章主要介绍了Spring Bean装载方式代码实例解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
Bean的装配方式
Bean的装配可以理解为依赖关系注入
基于XML的装配
a) 设值注入
i.要求：
- Bean 类必须提供一个默认的无参构造方法。
- Bean 类必须为需要注入的属性提供对应的setter方法。
b) 构造注入
package com.itheima.assemble;
import java.util.List;
public class User {
private String username;
private Integer password;
private List<String> List;
/*
* 1.使用构造注入
* 1.1提供所有带参数的有参构造方法
*/
public User(String username,Integer password,List<String> List){
super();
this.username = username;
this.password = password;
this.List = List;
}
/*
* 2.使用设值注入
* 2.1提供默认空构造方法
* 2.2为所有属性提供setter方法
*/
public User(){
}
public void setUsername(String username) {
this.username = username;
}
public void setPassword(Integer password) {
this.password = password;
}
public void setList(List<String> list) {
List = list;
}
@Override
/*
* (non-Javadoc)
* @see java.lang.Object#toString()
* 为了输出是看到结果，重写toString()方法
*/
public String toString() {
return "User [username=" + username + ", password=" + password + ", List=" + List + "]";
}
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- 1.使用构造注入方式装配User实例 -->
<bean id="user1" class="com.itheima.assemble.User">
<constructor-arg index="0" value="tom"></constructor-arg>
<constructor-arg index="1" value="123456"></constructor-arg>
<constructor-arg index="2">
<list>
<value>"constructorvalue1"</value>
<value>"constructorvalue2"</value>
</list>
</constructor-arg>
</bean>
<!-- 2.使用设值注入装配User实例 -->
<bean id="user2" class="com.itheima.assemble.User">
<property name="username" value="张三"></property>
<property name="password" value="654321"></property>
<!-- 注入list集合 -->
<property name="list">
<list>
<value>"setlistvalue1"</value>
<value>"setlistvalue2"</value>
</list>
</property>
</bean>
</beans>
<constructor -arg >元素用于定义构造方法的参数，子元素<Iist>来为Use r 类中对应的list集合属性注入值。
其中<property>元素用于调用Bean实例中的setter方法完成属性赋值，从而完成依赖注入。
package com.itheima.assemble;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class XmlBeanAssembleTest {
public static void main(String[] args) {
//定义配置文件路径
String xmlPath = "com/itheima/assemble/beans5.xml";
//加载配置文件
ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
//构造方式输出结果
System.out.println("构造方式：");
System.out.println(applicationContext.getBean("user1"));
//设值方式输出结果
System.out.println("设值方式：");
System.out.println(applicationContext.getBean("user2"));
}
}
2.基于Annotation的装配
package com.itheima.annotation;
public interface UserDao {
public void save();
}
package com.itheima.annotation;
import org.springframework.stereotype.Repository;
@Repository("userDao")
public class UserDaoImpl implements UserDao{
public void save(){
System.out.println("userdao...save...");
}
}
先使用@Repository 注解将UserDaolmpl 类标识为Spring 中的Bean，其写法相当于配置文件中<bean id="userDao" class="com.itheima.annotation.UserDaolmpl"/>
package com.itheima.annotation;
public interface UserService {
public void save();
}
package com.itheima.annotation;
import javax.annotation.Resource;
import org.springframework.stereotype.Service;
@Service("userService")
public class UserServiceImpl implements UserService{
@Resource(name="userDao")
private UserDao userDao;
@Override
public void save() {
// TODO Auto-generated method stub
//调用userDao中的save()方法
this.userDao.save();
System.out.println("userservice...save...");
}
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
}
@Service 注解将UserServicelmpl 类标识为Spring中的Bean,这相当于配置文件中<bean id="userService" class="com.itheima.annotation.UserServicelmpl”/> 的编写；然后使用@Resource 注解标注在属性userDao上，这相当于配置文件中<property name="userDao" ref="userDao“/>的写法。
package com.itheima.annotation;
import javax.annotation.Resource;
import org.springframework.stereotype.Controller;
@Controller("userController")
public class UserController {
@Resource(name="userService")
private UserService userService;
public void save(){
this.userService.save();
System.out.println("userControlle...save...");
}
public void setUserService(UserService userService) {
this.userService = userService;
}
}
Controller 注解标注了UserController 类，这相当于在配置文件中编写<bean id="userControll er" class="com .itheima.annotation.UserController"/>; 然后使用了@Resource 注解标注在userService 属性上，这相当于在配置文件中编写<propertyname="userService" ref="userService" />
<?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-4.3.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.3.xsd">
<!-- 使用context命名空间，在配置文件中开启相应的注释处理器 -->
<context:component-scan base-package="com.itheima.annotation"></context:component-scan>
</beans>
package com.itheima.annotation;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class AnnotationAssembleTest {
public static void main(String[] args) {
String xmlPath = "com/itheima/annotation/beans6.xml";
ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
//获取UserController实例
UserController userController = (UserController)applicationContext.getBean("userController");
//调用UserController中的save()方法
userController.save();
}
}
3.自动装配
<?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-4.3.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.3.xsd">
<!-- 使用bean元素的autowire属性完成自动装配 -->
<bean id="userDao" class="com.itheima.annotation.UserDaoImpl"></bean>
<bean id="userService" class="com.itheima.annotation.UserServiceImpl" autowire="byName"></bean>
<bean id="userController" class="com.itheima.annotation.UserController" autowire="byName"></bean>
</beans>
增加了autowire 属性，并将其属性值设置为byName 。在默认情况下，配置文件中需要通过ref 来装配Bean ，但设置了autowire=" byName"后，Spring 会自动寻找userServiceBean 中的属性，并将其属性名称与配置文件中定义的Bean 做匹配。由于UserServicelmpl 中定义了userDao 属'性及其setter 方法，这与配置文件中id 为userDao 的Bean 相匹配，所以Spring会自动地将id 为userDao 的Bean 装配到id 为userService 的Bean 中。
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