Spring学习七----------Bean的配置之自动装配

2022-11-01 07:44:44

Bean的自动装配（Autowiring）

no:不启用自动装配，此时需要手动注入。参考：Spring学习三----------注入方式

default：优先执行constructor，然后byType，最后byName

byName:根据属性名自动装配。此选项将检查容器并根据名字查找与属性完全一致的bean，并将其与属性自动装配

byType:如果容器中存在一个与指定属性类型相同的bean，那么将与该属性自动装配；如果存在多个该类型bean，那么跑出异常，并指出不能使用byType方式进行自动装配；如果没有找到相匹配的bean，则说明事都不发生

constructor:与byType方式类似，不同之处在于它应用于构造器参数。如果容器中没有找到与构造器参数类型一致的bean，那么抛出异常

1.项目结构

2.pom.xml

<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>org.springbean</groupId>

	<artifactId>Spring-AutoAssemble</artifactId>

	<packaging>jar</packaging>

	<version>0.0.1-SNAPSHOT</version>

	<name>Spring-AutoAssemble Maven Webapp</name>

	<url>http://maven.apache.org</url>

	<properties>

		<spring.version>4.3.7.RELEASE</spring.version>

	</properties>

	<dependencies>

		<!-- junit依赖 -->

		<dependency>

			<groupId>junit</groupId>

			<artifactId>junit</artifactId>

			<version>4.12</version>

			<scope>test</scope>

		</dependency>

		<!-- Spring核心依赖 -->

		<dependency>

		    <groupId>org.springframework</groupId>

		    <artifactId>spring-core</artifactId>

		    <version>${spring.version}</version>

		</dependency>

		<dependency>

		    <groupId>org.springframework</groupId>

		    <artifactId>spring-beans</artifactId>

		    <version>${spring.version}</version>

		</dependency><dependency>

		    <groupId>org.springframework</groupId>

		    <artifactId>spring-context</artifactId>

		    <version>${spring.version}</version>

		</dependency>

	</dependencies>

	<build>

		<finalName>Spring-AutoAssemble</finalName>

	</build>

</project>

3.AutowiringDao.java

package org.spring.autowiring.dao;

public interface AutowiringDao {

	public void say(String word);

}

4.AutowiringDaoImpl.java

package org.spring.autowiring.dao.impl;

import org.spring.autowiring.dao.AutowiringDao;

public class AutowiringDaoImpl implements AutowiringDao {

	public void say(String word) {

		System.out.println("AutowiringDaoImpl接受参数：" + word);

	}

}

5.AutowiringService.java

package org.spring.autowiring.service;

public interface AutowiringService {

	public void say(String word);

}

6.AutowiringServiceImpl.java

　　6.1 byName和byType

package org.spring.autowiring.service.impl;

import org.spring.autowiring.dao.AutowiringDao;

import org.spring.autowiring.service.AutowiringService;

public class AutowiringServiceImpl implements AutowiringService {

	//byName时，必须与bean配置的id一致；byType时，可随意命名。本次修改bean的id，不再修改该属性名；效果一样

	private AutowiringDao autowiringDao;

	/**

	 * (byName和byType)只需setter方法

	 * @param autowiringDao

	 */

	public void setAutowiringDao(AutowiringDao autowiringDao) {

		this.autowiringDao = autowiringDao;

	}

	public void say(String word) {

		System.out.println("AutowiringServiceImpl接受参数:" + word);

		autowiringDao.say(word);

	}

}

　　6.2 constructor

package org.spring.autowiring.service.impl;

import org.spring.autowiring.dao.AutowiringDao;

import org.spring.autowiring.service.AutowiringService;

public class AutowiringServiceImpl implements AutowiringService {

	private AutowiringDao autowiringDao;

	/**

	 * constructor时存在；byName和byType时存在会报错

	 *

	 * @param autowiringDao

	 */

	public AutowiringServiceImpl(AutowiringDao autowiringDao) {

		this.autowiringDao = autowiringDao;

	}

	public void say(String word) {

		System.out.println("AutowiringServiceImpl接受参数:" + word);

		autowiringDao.say(word);

	}

}

7.spring-autowiring.xml（三选一）

　　7.1 byName

<?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"

        default-autowire="byName">

    <bean id="autowiringService" class="org.spring.autowiring.service.impl.AutowiringServiceImpl"/>

    <bean id="autowiringDao" class="org.spring.autowiring.dao.impl.AutowiringDaoImpl"/>

</beans>

　　7.2 byType和constructor

<?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"

        default-autowire="byType">

    <bean id="autowiringService" class="org.spring.autowiring.service.impl.AutowiringServiceImpl"/>

    <bean class="org.spring.autowiring.dao.impl.AutowiringDaoImpl"/>

</beans>

8.JunitTestBase.java

package org.spring.autowiring.test;

import org.junit.After;

import org.junit.Before;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import org.springframework.util.StringUtils;

/**

 * 单元测试基类

 *

 */

public class JunitTestBase {

	private ClassPathXmlApplicationContext context;

	private String springXmlPath;

	/**

	 * 无参构造器，使用此构造器创建对象，使用默认spring配置文件

	 */

	public JunitTestBase() {

	}

	/**

	 * 含参构造器，初始化spring配置文件路径

	 *

	 * @param springXmlPath

	 * 							spring配置文件路径

	 */

	public JunitTestBase(String springXmlPath) {

		this.springXmlPath = springXmlPath;

	}

	/**

	 * 启动spring容器，在@Test方法执行之前执行

	 */

	@Before

	public void start() {

		if(StringUtils.isEmpty(springXmlPath)) {//设置默认spring配置文件路径

			springXmlPath = "classpath:spring-*.xml";

		}

		//加载spring配置文件到spring容器中

		context = new ClassPathXmlApplicationContext(springXmlPath.split("[,\\s]+"));

		//启动spring容器，并扩散启动信号到该容器下的所有组件

		context.start();

	}

	/**

	 * 销毁spring容器，在@Test方法执行之前执行

	 */

	@After

	public void stop() {

		if(context != null){

			context.destroy();

		}

	}

	/**

	 * 通过bean id获取bean对象

	 *

	 * @param beanId

	 * 					bean id

	 * @return

	 */

	public Object getBean(String beanId) {

		return context.getBean(beanId);

	}

}

9.TestAutowiring.java

package org.spring.autowiring.test;

import org.junit.Test;

import org.spring.autowiring.service.AutowiringService;

public class TestAutowiring extends JunitTestBase {

	/**

	 * 通过构造器传递spring配置文件路径

	 */

	public TestAutowiring() {

		super("classpath:spring-autowiring.xml");

	}

	@Test

	public void testAutowiring() {

		AutowiringService autowiringService =

					(AutowiringService) super.getBean("autowiringService");

		autowiringService.say("test");

	}

}

10.效果预览

　　10.1 byName或byType(AutowiringServiceImpl.java中含有自定义构造器时)

　　10.2 byName(AutowiringServiceImpl.java中不含有自定义构造器时)

　　10.3 byType(spring-autowiring.xml中dao层配置的bean中id不存在时)

　　10.4 byType(spring-autowiring.xml中dao层配置的bean中id存在时)---只是样式不一样而已。。。

　　10.5 constructor

更多测试情况，可自行测试。

参考：http://www.imooc.com/video/3757

码农公寓

相关文章