spring入门（8）--装配Bean之自动装配

于 2013-04-25 21:46:00 发布 · 102 阅读 · 0
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#java

本文详细介绍了Spring框架中自动装配的四种方式：no、byName、byType和constructor，并通过具体案例展示了不同配置下依赖注入的行为。

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Spring_Autowiringcollaborators

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

<beanid="foo"class="...Foo"autowire="autowiretype">

Mode Explanation

no:(Default)Noautowiring.Beanreferencesmustbedefinedviaarefelement.

Changingthedefaultsettingisnotrecommendedforlargerdeployments,

becausespecifyingcollaboratorsexplicitlygivesgreatercontrolandclarity.

Tosomeextent,itdocumentsthestructureofasystem.

byName:Autowiringbypropertyname.

Springlooksforabeanwiththesamenameasthepropertythatneedstobeautowired.

Forexample,ifabeandefinitionissettoautowirebyname,

anditcontainsamasterproperty(thatis,ithasasetMaster(..)method),

Springlooksforabeandefinitionnamedmaster,andusesittosettheproperty.

byType:Allowsapropertytobeautowiredifexactlyonebeanofthepropertytypeexistsinthecontainer.

Ifmorethanoneexists,afatalexceptionisthrown,

whichindicatesthatyoumaynotusebyTypeautowiringforthatbean.

Iftherearenomatchingbeans,nothinghappens;thepropertyisnotset.

constructor：AnalogoustobyType,butappliestoconstructorarguments.

Ifthereisnotexactlyonebeanoftheconstructorargumenttypeinthecontainer,afatalerrorisraised

案例分析：

1、创建CumputerBean类

[java] view plain copy print ?
  1. packagewww.csdn.spring.autowire.bean;
  3. publicclassCumputerBean{
  5. //电脑名称
  7. privateStringname;
  9. publicvoidsetName(Stringname){
  11. this.name=name;
  13. }
  15. }
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

[java] view plain copy print ?
  1. packagewww.csdn.spring.autowire.bean;
  4. publicclassDeptBean{
  6. //部门名称
  8. privateStringname;
  10. publicvoidsetName(Stringname){
  12. this.name=name;
  14. }
  16. }
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

[java] view plain copy print ?
  1. packagewww.csdn.spring.autowire.bean;
  4. publicclassEmployeeBean{
  6. privateDeptBeandeptBean;
  8. privateCumputerBeancumputerBean;
  11. publicvoidsetDeptBean(DeptBeandeptBean){
  13. this.deptBean=deptBean;
  15. }
  17. publicvoidsetCumputerBean(CumputerBeancumputerBean){
  19. this.cumputerBean=cumputerBean;
  21. }
  23. @Override
  25. publicStringtoString(){
  27. return"EmployeeBean[deptBean="+deptBean+",cumputerBean="
  29. +cumputerBean+"]";
  31. }
  34. }
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）

[java] view plain copy print ?
  1. <?xmlversion="1.0"encoding="UTF-8"?>
  3. <beansxmlns="http://www.springframework.org/schema/beans"
  4. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  5. xsi:schemaLocation="http://www.springframework.org/schema/beans
  6. http://www.springframework.org/schema/beans/spring-beans.xsd">
  8. <!--电脑bean-->
  9. <beanid="cumputerBean"class="www.csdn.spring.autowire.bean.CumputerBean">
  10. <propertyname="name"value="HP6325笔记本"/>
  11. </bean>
  13. <!--部门bean-->
  14. <beanid="deptBean"class="www.csdn.spring.autowire.bean.DeptBean">
  15. <propertyname="name"value="优快云教育事业部"/>
  16. </bean>
  18. <!--员工bean根据EmployeeBean中的属性名称去匹配-->
  19. <beanid="employeeBean"class="www.csdn.spring.autowire.bean.EmployeeBean">
  20. <propertyname="cumputerBean"ref="cumputerBean"/>
  21. <propertyname="deptBean"ref="deptBean"/>
  23. </bean>
  25. </beans>
<?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="优快云教育事业部" />
</bean>

<!-- 员工bean  根据EmployeeBean中的 属性名称  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)

[java] view plain copy print ?
  1. <?xmlversion="1.0"encoding="UTF-8"?>
  3. <beansxmlns="http://www.springframework.org/schema/beans"
  5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  7. xsi:schemaLocation="http://www.springframework.org/schema/beans
  9. http://www.springframework.org/schema/beans/spring-beans.xsd">
  13. <!--电脑bean-->
  15. <beanid="cumputerBean"class="www.csdn.spring.autowire.bean.CumputerBean">
  17. <propertyname="name"value="HP6325笔记本"/>
  19. </bean>
  21. <!--部门bean-->
  23. <beanid="deptBean"class="www.csdn.spring.autowire.bean.DeptBean">
  25. <propertyname="name"value="优快云教育事业部"/>
  27. </bean>
  29. <!--员工bean-->
  31. <beanid="employeeBean"class="www.csdn.spring.autowire.bean.EmployeeBean"autowire="byName"/>
  33. </beans>
<?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="优快云教育事业部" />

</bean>

<!-- 员工bean-->

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

</beans>
[java] view plain copy print ?

3、byType配置(分析:会根据EmployeeBean中属性的类型自动装配)

[java] view plain copy print ?
  1. <?xmlversion="1.0"encoding="UTF-8"?>
  3. <beansxmlns="http://www.springframework.org/schema/beans"
  5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  7. xsi:schemaLocation="http://www.springframework.org/schema/beans
  9. http://www.springframework.org/schema/beans/spring-beans.xsd">
  11. <!--电脑bean-->
  13. <beanid="cumputerBean"class="www.csdn.spring.autowire.bean.CumputerBean">
  15. <propertyname="name"value="HP6325笔记本"/>
  17. </bean>
  19. <!--部门bean-->
  21. <beanid="deptBean"class="www.csdn.spring.autowire.bean.DeptBean">
  23. <propertyname="name"value="优快云教育事业部"/>
  25. </bean>
  27. <!--员工bean根据EmployeeBean中的属性名称去匹配-->
  29. <beanid="employeeBean"class="www.csdn.spring.autowire.bean.EmployeeBean"autowire="byType"/>
  32. </beans>
<?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="优快云教育事业部" />

</bean>

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

<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:

Errorcreatingbeanwithname'employeeBean'definedinclasspathresource[spring-byType.xml]:Unsatisfieddependencyexpressedthroughbeanproperty'deptBean'::

Noqualifyingbeanoftype[www.csdn.spring.autowire.bean.DeptBean]isdefined:expectedsinglematchingbeanbutfound2:deptBean,deptBean1;

nestedexceptionisorg.springframework.beans.factory.NoUniqueBeanDefinitionException:

Noqualifyingbeanoftype[www.csdn.spring.autowire.bean.DeptBean]isdefined:expectedsinglematchingbeanbutfound2: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：

[java] view plain copy print ?
  1. packagewww.csdn.spring.autowire.bean;
  4. publicclassEmployeeBean{
  6. privateDeptBeandeptBean;
  7. privateCumputerBeancumputerBean;
  10. publicEmployeeBean(DeptBeandeptBean,CumputerBeancumputerBean){
  11. super();
  12. this.deptBean=deptBean;
  13. this.cumputerBean=cumputerBean;
  14. }
  16. @Override
  17. publicStringtoString(){
  18. return"EmployeeBean[deptBean="+deptBean+",cumputerBean="
  19. +cumputerBean+"]";
  20. }
  21. }
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 + "]";
}
}
[java] view plain copy print ?

配置文件操作：

[html] view plain copy print ?
  1. <?xmlversion="1.0"encoding="UTF-8"?>
  3. <beansxmlns="http://www.springframework.org/schema/beans"
  5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  7. xsi:schemaLocation="http://www.springframework.org/schema/beans
  9. http://www.springframework.org/schema/beans/spring-beans.xsd">
  11. <!--电脑bean-->
  13. <beanid="cumputerBean"class="www.csdn.spring.autowire.bean.CumputerBean">
  14. <propertyname="name"value="HP6325笔记本"/>
  15. </bean>
  17. <!--部门bean-->
  19. <beanid="deptBean"class="www.csdn.spring.autowire.bean.DeptBean">
  20. <propertyname="name"value="优快云教育事业部"/>
  21. </bean>
  23. <!--员工bean根据EmployeeBean中的属性名称bytype去匹配-->
  24. <beanid="employeeBean"class="www.csdn.spring.autowire.bean.EmployeeBean"
  25. autowire="constructor">
  26. </bean>
  28. </beans> 
  <?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="优快云教育事业部" />
</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

[html] view plain copy print ?
  1. <?xmlversion="1.0"encoding="UTF-8"?>
  3. <beansxmlns="http://www.springframework.org/schema/beans"
  5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  7. xsi:schemaLocation="http://www.springframework.org/schema/beans
  9. http://www.springframework.org/schema/beans/spring-beans.xsd">
  11. <!--电脑bean-->
  13. <beanid="cumputerBean"class="www.csdn.spring.autowire.bean.CumputerBean">
  15. <propertyname="name"value="HP6325笔记本"/>
  17. </bean>
  19. <!--员工bean根据EmployeeBean中的属性名称bytype去匹配-->
  21. <beanid="employeeBean"class="www.csdn.spring.autowire.bean.EmployeeBean"
  23. autowire="constructor">
  25. </bean>
  27. </beans> 
<?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>
[html] view plain copy print ?

会出现如下bug:

org.springframework.beans.factory.UnsatisfiedDependencyException:

Errorcreatingbeanwithname'employeeBean'definedinclasspathresource[spring-constructors.xml]:Unsatisfieddependencyexpressedthroughconstructorargumentwithindex0oftype[www.csdn.spring.autowire.bean.DeptBean]::

Noqualifyingbeanoftype[www.csdn.spring.autowire.bean.DeptBean]foundfordependency:

expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{};

nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException:

Noqualifyingbeanoftype[www.csdn.spring.autowire.bean.DeptBean]foundfordependency:

expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{}

Causedby:

org.springframework.beans.factory.NoSuchBeanDefinitionException:

Noqualifyingbeanoftype[www.csdn.spring.autowire.bean.DeptBean]foundfordependency:

expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{}

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：

[html] view plain copy print ?
  1. <?xmlversion="1.0"encoding="UTF-8"?>
  3. <beansxmlns="http://www.springframework.org/schema/beans"
  5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  7. xsi:schemaLocation="http://www.springframework.org/schema/beans
  9. http://www.springframework.org/schema/beans/spring-beans.xsd">
  11. <!--电脑bean-->
  13. <beanid="cumputerBean"class="www.csdn.spring.autowire.bean.CumputerBean">
  15. <propertyname="name"value="HP6325笔记本"/>
  17. </bean>
  19. <!--部门bean-->
  21. <beanid="deptBean"class="www.csdn.spring.autowire.bean.DeptBean">
  23. <propertyname="name"value="优快云教育事业部"/>
  25. </bean>
  27. <!--部门bean-->
  29. <beanid="deptBean1"class="www.csdn.spring.autowire.bean.DeptBean">
  31. <propertyname="name"value="优快云教育事业部"/>
  33. </bean>
  36. <!--员工bean根据EmployeeBean中的属性名称bytype去匹配-->
  38. <beanid="employeeBean"class="www.csdn.spring.autowire.bean.EmployeeBean"
  40. autowire="constructor">
  42. </bean>
  44. </beans> 
<?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="优快云教育事业部" />

</bean>

<!-- 部门bean -->

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

<property name="name" value="优快云教育事业部" />

</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：

[html] view plain copy print ?
  1. <?xmlversion="1.0"encoding="UTF-8"?>
  3. <beansxmlns="http://www.springframework.org/schema/beans"
  5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  7. xsi:schemaLocation="http://www.springframework.org/schema/beans
  9. http://www.springframework.org/schema/beans/spring-beans.xsd">
  11. <!--电脑bean-->
  13. <beanid="cumputerBean"class="www.csdn.spring.autowire.bean.CumputerBean">
  15. <propertyname="name"value="HP6325笔记本"/>
  17. </bean>
  19. <!--部门bean-->
  21. <beanid="deptBean1"class="www.csdn.spring.autowire.bean.DeptBean">
  23. <propertyname="name"value="优快云教育事业部"/>
  25. </bean>
  27. <!--部门bean-->
  29. <beanid="deptBean2"class="www.csdn.spring.autowire.bean.DeptBean">
  31. <propertyname="name"value="优快云教育事业部"/>
  33. </bean>
  35. <!--员工bean根据EmployeeBean中的属性名称bytype去匹配-->
  37. <beanid="employeeBean"class="www.csdn.spring.autowire.bean.EmployeeBean"
  39. autowire="constructor">
  41. </bean>
  43. </beans> 
<?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="优快云教育事业部" />

</bean>

<!-- 部门bean -->

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

<property name="name" value="优快云教育事业部" />

</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）:

[java] view plain copy print ?
  1. org.springframework.beans.factory.UnsatisfiedDependencyException:
  3. Errorcreatingbeanwithname'employeeBean'definedinclasspathresource[spring-constructors.xml]: 
org.springframework.beans.factory.UnsatisfiedDependencyException: 

Error creating bean with name 'employeeBean' defined in class path resource [spring-constructors.xml]:
[java] view plain copy print ?
  1. Unsatisfieddependencyexpressedthroughconstructorargumentwithindex0oftype[www.csdn.spring.autowire.bean.DeptBean]::
  3. Noqualifyingbeanoftype[www.csdn.spring.autowire.bean.DeptBean]isdefined:
  5. expectedsinglematchingbeanbutfound2:deptBean1,deptBean2;
  7. nestedexceptionisorg.springframework.beans.factory.NoUniqueBeanDefinitionException:
  9. Noqualifyingbeanoftype[www.csdn.spring.autowire.bean.DeptBean]isdefined:
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:
[java] view plain copy print ?
  1. expectedsinglematchingbeanbutfound2:deptBean1,deptBean2
iteye_8029
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