bean依赖注入三种方式

bean依赖注入的三种方式如下：

1. 构造方法注入
2. set方法注入
3. P命名空间注入

此处演示的项目结构如下：

方法一： 构造方法注入
UserDaoImpl.java

public class UserDaoImpl implements IUserDao {@Overridepublic void save() {System.out.println("save方法执行成功...");}
}

UserServiceImpl.java

public class UserServiceImpl implements IUserService {private IUserDao userDao;public UserServiceImpl(IUserDao userDao) {this.userDao = userDao;}@Overridepublic void save() {userDao.save();}
}

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd"xmlns:p="http://www.springframework.org/schema/p"><bean id="userDao" class="com.hy.dao.impl.UserDaoImpl" /><bean id="userService" class="com.hy.service.impl.UserServiceImpl"><constructor-arg name="userDao" ref="userDao" />bean>beans>

TestDependencyInjection.java

public class TestDependencyInjection {/*** 方式一、构造方法注入*/@Testpublic void test1(){ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");IUserService userService = (IUserService) applicationContext.getBean("userService");userService.save();}
}

输出结果

UserDao.java和TestDependencyInjection.java代码一致，下面的方法二和方法三省略此处

方法二、set方法注入
UserServiceImpl.java

public class UserServiceImpl implements IUserService {private IUserDao userDao;public void setUserDao(IUserDao userDao) {this.userDao = userDao;}@Overridepublic void save() {userDao.save();}
}

applicationContext.xml

<bean id="userDao" class="com.hy.dao.impl.UserDaoImpl" />
<bean id="userService" class="com.hy.service.impl.UserServiceImpl"><property name="userDao" ref="userDao" />
bean>

其中property标签中的name属性值为UserServiceImplz类中的userDao字段
方法三：P命名空间注入(原理也是set方法注入)
applicationContext.xml首先引入P命名空间

xmlns:p="http://www.springframework.org/schema/p"

UserServiceImpl.java

public class UserServiceImpl implements IUserService {private IUserDao userDao;public void setUserDao(IUserDao userDao) {this.userDao = userDao;}@Overridepublic void save() {userDao.save();}
}

applicationContext.xml

<bean id="userDao" class="com.hy.dao.impl.UserDaoImpl" />
<bean id="userService" class="com.hy.service.impl.UserServiceImpl" p:userDao="userDao" p:userDao-ref="userDao" />

详细代码地址如下：详细代码地址

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