Spring3.2.2_自动装配

Spring3.2.2_自动装配

分类： Spring课程总结 2013-04-25 16:33  157人阅读  评论(0)  收藏  举报

Spring_Autowiring collaborators

在Spring3.2.2中自动装配类型，分别为：no(default)(不采用自动装配)、byName，byType，constructor下面来分别介绍一下这些是如何自动装配的

   <bean id="foo" class="...Foo" autowire="autowire type">

Mode            Explanation

no: (Default) No autowiring. Bean references must be defined via a ref element. 

Changing the default setting is not recommended for larger deployments,

 because specifying collaborators explicitly gives greater control and clarity. 

To some extent, it documents the structure of a system.

 

byName:Autowiring by property name. 

Spring looks for a bean with the same name as the property that needs to be autowired. 

For example, if a bean definition is set to autowire by name, 

and it contains a master property (that is, it has a setMaster(..) method),

 Spring looks for a bean definition named master, and uses it to set the property.

 

byType:Allows a property to be autowired if exactly one bean of the property type exists in the container.

 If more than one exists, a fatal exception is thrown, 

which indicates that you may not use byType autowiring for that bean.

 If there are no matching beans, nothing happens; the property is not set.

 

constructor：Analogous to byType, but applies to constructor arguments.

 If there is not exactly one bean of the constructor argument type in the container, a fatal error is raised

案例分析：

  1、创建CumputerBean类

package www.csdn.spring.autowire.bean;

public class CumputerBean {

// 电脑名称

private String name;

public void setName(String name) {

this.name = name;

}

}

2、创建DeptBean 类

package www.csdn.spring.autowire.bean;


public class DeptBean {

//部门名称

private String name;

public void setName(String name) {

this.name = name;

}

}

3、创建EmployeeBean

package www.csdn.spring.autowire.bean;


public class EmployeeBean {

private DeptBean deptBean;

private CumputerBean cumputerBean;


public void setDeptBean(DeptBean deptBean) {

this.deptBean = deptBean;

}

public void setCumputerBean(CumputerBean cumputerBean) {

this.cumputerBean = cumputerBean;

}

@Override

public String toString() {

return "EmployeeBean [deptBean=" + deptBean + ", cumputerBean="

+ cumputerBean + "]";

}


}

首先分析no、byName、byType的配置都是采用setter方法依赖注入实现的案例

1、no配置（通过ref=””引用需要的bean）

<?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">

<!-- 电脑bean -->
<bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">
<property name="name" value="HP6325笔记本" />
</bean>

<!-- 部门bean -->
<bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">
<property name="name" value="CSDN教育事业部" />
</bean>

<!-- 员工bean  根据EmployeeBean中的属性名称通过ref="bean"去匹配-->
<bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean">
<property name="cumputerBean" ref="cumputerBean" />
<property name="deptBean" ref="deptBean" />

</bean>

</beans>

2、byName配置(分析:会根据EmployeeBean中属性的名称 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"

xsi:schemaLocation="http://www.springframework.org/schema/beans

           http://www.springframework.org/schema/beans/spring-beans.xsd">



<!-- 电脑bean -->

<bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">

<property name="name" value="HP6325笔记本" />

</bean>

<!-- 部门bean -->

<bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">

<property name="name" value="CSDN教育事业部" />

</bean>

<!-- 员工bean-->

<bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean" autowire="byName"/>

</beans>

3、byType配置(分析:会根据EmployeeBean中属性的类型 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"

xsi:schemaLocation="http://www.springframework.org/schema/beans

           http://www.springframework.org/schema/beans/spring-beans.xsd">

<!-- 电脑bean -->

<bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">

<property name="name" value="HP6325笔记本" />

</bean>

<!-- 部门bean -->

<bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">

<property name="name" value="CSDN教育事业部" />

</bean>

<!-- 员工bean  根据EmployeeBean中的属性根据类型匹配-->

<bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean" autowire="byType"/>


</beans>

注意：当根据byType类型装配时，当在容器内找到多个匹配的类型时会出现如下bug

org.springframework.beans.factory.UnsatisfiedDependencyException: 

Error creating bean with name 'employeeBean' defined in class path resource [spring-byType.xml]: Unsatisfied dependency expressed through bean property 'deptBean': :

 No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] is defined: expected single matching bean but found 2: deptBean,deptBean1; 

nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: 

No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] is defined: expected single matching bean but found 2: deptBean,deptBean1

 

4、Constructor(构造器参数根据byType类型匹配，自动装配)

首先修改EmployeeBean类 修改后代码如下：

package www.csdn.spring.autowire.bean;


public class EmployeeBean {

private DeptBean deptBean;
private CumputerBean cumputerBean;


public EmployeeBean(DeptBean deptBean, CumputerBean cumputerBean) {
super();
this.deptBean = deptBean;
this.cumputerBean = cumputerBean;
}

@Override
public String toString() {
return "EmployeeBean [deptBean=" + deptBean + ", cumputerBean="
+ cumputerBean + "]";
}
}

配置文件操作：

  <?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">

<!-- 电脑bean -->

<bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">
<property name="name" value="HP6325笔记本" />
</bean>

<!-- 部门bean -->

<bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">
<property name="name" value="CSDN教育事业部" />
</bean>

<!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->
<bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"
autowire="constructor">
</bean>

</beans>

说明:

1、当构造器的参数类型在容器中找不全时。

 比如：

   配置文件中只配置了CumpterBean时

 

  

<?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">

<!-- 电脑bean -->

<bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">

<property name="name" value="HP6325笔记本" />

</bean>

<!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->

<bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"

autowire="constructor">

</bean>

</beans>

会出现如下bug:

org.springframework.beans.factory.UnsatisfiedDependencyException:

 Error creating bean with name 'employeeBean' defined in class path resource [spring-constructors.xml]: Unsatisfied dependency expressed through constructor argument with index 0 of type [www.csdn.spring.autowire.bean.DeptBean]: : 

No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] found for dependency:

 expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}; 

nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException:

 No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] found for dependency: 

expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}

Caused by: 

org.springframework.beans.factory.NoSuchBeanDefinitionException:

 No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] found for dependency: 

expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}

2、当配置文件找到构造器参数的类型有多个的时候比如配置文件如下：

<?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">

<!-- 电脑bean -->

<bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">

<property name="name" value="HP6325笔记本" />

</bean>

<!-- 部门bean -->

<bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">

<property name="name" value="CSDN教育事业部" />

</bean>

<!-- 部门bean -->

<bean id="deptBean1" class="www.csdn.spring.autowire.bean.DeptBean">

<property name="name" value="CSDN教育事业部" />

</bean>


<!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->

<bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"

autowire="constructor">

</bean>

</beans>

 

说明：上面配置有两个同样类型的DeptBean但是不会出现bug，原因是在EmployeeBean中构造器接受的参数名称与deptBean一致。

3、当配置文件找到构造器参数的类型有多个的时候比如配置文件如下：

<?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">

<!-- 电脑bean -->

<bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">

<property name="name" value="HP6325笔记本" />

</bean>

<!-- 部门bean -->

<bean id="deptBean1" class="www.csdn.spring.autowire.bean.DeptBean">

<property name="name" value="CSDN教育事业部" />

</bean>

<!-- 部门bean -->

<bean id="deptBean2" class="www.csdn.spring.autowire.bean.DeptBean">

<property name="name" value="CSDN教育事业部" />

</bean>

<!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->

<bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"

autowire="constructor">

</bean>

</beans>

会出现如下bug（与byType的bug一致）:

org.springframework.beans.factory.UnsatisfiedDependencyException:

Error creating bean with name 'employeeBean' defined in class path resource [spring-constructors.xml]:

Unsatisfied dependency expressed through constructor argument with index 0 of type [www.csdn.spring.autowire.bean.DeptBean]: :

No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] is defined:

expected single matching bean but found 2: deptBean1,deptBean2;

nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException:

 No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] is defined:

expected single matching bean but found 2: deptBean1,deptBean2