技術標籤：Spring Frameworkspringspring自動裝配ByNameByType

Spring Bean 自動裝配

spring自動裝配可以簡化spring配置。

<bean> 元素的 autowire 屬性。autowire 屬性有五個值

自動裝配的5中型別

ByName自動裝配

Java程式碼

public class User {
	private String name;
	public User(String name) {
		this.name = name;
	}
	public String getName() {
		return name;
	}
	public void
 
 setName(String name) {
		this.name = name;
	}
	@Override
	public String toString() {
		return "User name=" + name ;
	}
}

public class UserDaoImpl implements UserDao{
	@Override
	public User getUser() {
		return new User("自動裝配ByName");
	}
}

public class UserServiceImpl implements
 
 UserService{
	private UserDao userDao;
	public UserDao getUserDao() {
		return userDao;
	}
	public void setUserDao(UserDao userDao) {
		this.userDao = userDao;
	}
	@Override
	public User getUser() {
		return userDao.getUser();
	}
}


public class TestSpringAutowire {
	public static void main(String[] args) {
		ApplicationContext act= new ClassPathXmlApplicationContext("/config/spring.xml");
		UserServiceImpl userService=(UserServiceImpl)act.getBean("userService");
		User user = userService.getUser();
		System.out.println(user.getName());
	}
}

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:p="http://www.springframework.org/schema/p"
	xmlns:c="http://www.springframework.org/schema/c"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
	<bean id ="userDao" class="cn.lingyiwin.dao.impl.UserDaoImpl"/>
	<bean id ="userService" class="cn.lingyiwin.service.impl.UserServiceImpl" autowire="byName"/>
</beans>

<!--或-->

<?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:p="http://www.springframework.org/schema/p"
	xmlns:c="http://www.springframework.org/schema/c"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd" default-autowire="byName">
	<bean id ="userDao" class="cn.lingyiwin.dao.impl.UserDaoImpl"/>
	<bean id ="userService" class="cn.lingyiwin.service.impl.UserServiceImpl"/>
</beans>

執行結果：

注意：ByName自動裝配 service 中的userDao 是通過set方法設定的，xml中userDao要和sevice中屬性名稱一樣。

ByType自動裝配（一般不用）

<?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:p="http://www.springframework.org/schema/p"
	xmlns:c="http://www.springframework.org/schema/c"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
        
	<bean class="cn.lingyiwin.dao.impl.UserDaoImpl"/>
	<bean id ="userService" class="cn.lingyiwin.service.impl.UserServiceImpl" autowire="byType"/>
</beans>

注意：通過型別裝配，需要確保型別只有一個，如果有多個型別，就報錯了，舉例如下：

UserDao增加一個實現類：

public class UserDaoMySqlImpl implements UserDao{
	@Override
	public User getUser() {
		return null;
	}
}

xml注入

<?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:p="http://www.springframework.org/schema/p"
	xmlns:c="http://www.springframework.org/schema/c"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
        
	<bean class="cn.lingyiwin.dao.impl.UserDaoImpl"/>
	<bean class="cn.lingyiwin.dao.impl.UserDaoMySqlImpl"/>
	<bean id ="userService" class="cn.lingyiwin.service.impl.UserServiceImpl" autowire="byType"/>
</beans>

執行結果：

警告: Exception encountered during context initialization - cancelling refresh attempt
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userService' defined in class path resource [config/spring.xml]: Unsatisfied dependency expressed through bean property 'userDao': : No qualifying bean of type [cn.lingyiwin.dao.UserDao] is defined: expected single matching bean but found 2: cn.lingyiwin.dao.impl.UserDaoImpl#0,cn.lingyiwin.dao.impl.UserDaoMySqlImpl#0; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [cn.lingyiwin.dao.UserDao] is defined: expected single matching bean but found 2: cn.lingyiwin.dao.impl.UserDaoImpl#0,cn.lingyiwin.dao.impl.UserDaoMySqlImpl#0
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireByType(AbstractAutowireCapableBeanFactory.java:1303)

constructor 裝配

修改java程式碼：

public class UserServiceImpl implements UserService{
	private UserDao userDao;
	public UserServiceImpl(UserDao userDao) {
		this.userDao = userDao;
	}
	@Override
	public User getUser() {
		return userDao.getUser();
	}
}

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:p="http://www.springframework.org/schema/p"
	xmlns:c="http://www.springframework.org/schema/c"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
        
	<bean class="cn.lingyiwin.dao.impl.UserDaoImpl"/>
	<bean id ="userService" class="cn.lingyiwin.service.impl.UserServiceImpl" autowire="constructor"/>
</beans>

執行結果：