Spring3.2.2_自动装配

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Spring3.2.2_自动装配

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

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：

、创建CumputerBean类

1. package www.csdn.spring.autowire.bean;  
2.   
3. public class CumputerBean {  
4.   
5. // 电脑名称  
6.   
7. private String name;  
8.   
9. public void setName(String name) {  
10.   
11. this.name = name;  
12.   
13. }  
14.   
15. }

2、创建DeptBean 类

1. package www.csdn.spring.autowire.bean;  
2.   
3.   
4. public class DeptBean {  
5.   
6. //部门名称  
7.   
8. private String name;  
9.   
10. public void setName(String name) {  
11.   
12. this.name = name;  
13.   
14. }  
15.   
16. }

3、创建EmployeeBean

1. package www.csdn.spring.autowire.bean;  
2.   
3.   
4. public class EmployeeBean {  
5.   
6. private DeptBean deptBean;  
7.   
8. private CumputerBean cumputerBean;  
9.   
10.   
11. public void setDeptBean(DeptBean deptBean) {  
12.   
13. this.deptBean = deptBean;  
14.   
15. }  
16.   
17. public void setCumputerBean(CumputerBean cumputerBean) {  
18.   
19. this.cumputerBean = cumputerBean;  
20.   
21. }  
22.   
23. @Override  
24.   
25. public String toString() {  
26.   
27. return "EmployeeBean [deptBean=" + deptBean + ", cumputerBean="  
28.   
29. + cumputerBean + "]";  
30.   
31. }  
32.   
33.   
34. }

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）

1. <?xml version="1.0" encoding="UTF-8"?>  
2.   
3. <beans xmlns="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. //www.springframework.org/schema/beans/spring-beans.xsd">  
7.   
8. <!-- 电脑bean -->  
9. <bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">  
10. <property name="name" value="HP6325笔记本" />  
11. </bean>  
12.   
13. <!-- 部门bean -->  
14. <bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">  
15. <property name="name" value="CSDN教育事业部" />  
16. </bean>  
17.   
18. <!-- 员工bean  根据EmployeeBean中的属性名称通过ref="bean"去匹配-->  
19. <bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean">  
20. <property name="cumputerBean" ref="cumputerBean" />  
21. <property name="deptBean" ref="deptBean" />  
22.   
23. </bean>  
24.   
25. </beans>

2、byName配置(分析:会根据EmployeeBean中属性的名称自动装配)

1. <?xml version="1.0" encoding="UTF-8"?>  
2.   
3. <beans xmlns="http://www.springframework.org/schema/beans"  
4.   
5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
6.   
7. xsi:schemaLocation="http://www.springframework.org/schema/beans  
8.   
9. //www.springframework.org/schema/beans/spring-beans.xsd">  
10.   
11.   
12.   
13. <!-- 电脑bean -->  
14.   
15. <bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">  
16.   
17. <property name="name" value="HP6325笔记本" />  
18.   
19. </bean>  
20.   
21. <!-- 部门bean -->  
22.   
23. <bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">  
24.   
25. <property name="name" value="CSDN教育事业部" />  
26.   
27. </bean>  
28.   
29. <!-- 员工bean-->  
30.   
31. <bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean" autowire="byName"/>  
32.   
33. </beans>

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

1. <?xml version="1.0" encoding="UTF-8"?>  
2.   
3. <beans xmlns="http://www.springframework.org/schema/beans"  
4.   
5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
6.   
7. xsi:schemaLocation="http://www.springframework.org/schema/beans  
8.   
9. //www.springframework.org/schema/beans/spring-beans.xsd">  
10.   
11. <!-- 电脑bean -->  
12.   
13. <bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">  
14.   
15. <property name="name" value="HP6325笔记本" />  
16.   
17. </bean>  
18.   
19. <!-- 部门bean -->  
20.   
21. <bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">  
22.   
23. <property name="name" value="CSDN教育事业部" />  
24.   
25. </bean>  
26.   
27. <!-- 员工bean  根据EmployeeBean中的属性根据类型匹配-->  
28.   
29. <bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean" autowire="byType"/>  
30.   
31.   
32. </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：

1. package www.csdn.spring.autowire.bean;  
2.   
3.   
4. public class EmployeeBean {  
5.   
6. private DeptBean deptBean;  
7. private CumputerBean cumputerBean;  
8.   
9.   
10. public EmployeeBean(DeptBean deptBean, CumputerBean cumputerBean) {  
11. super();  
12. this.deptBean = deptBean;  
13. this.cumputerBean = cumputerBean;  
14. }  
15.   
16. @Override  
17. public String toString() {  
18. return "EmployeeBean [deptBean=" + deptBean + ", cumputerBean="  
19. + cumputerBean + "]";  
20. }  
21. }

配置文件操作：

1.   <?xml version="1.0" encoding="UTF-8"?>  
2.   
3. <beans xmlns="http://www.springframework.org/schema/beans"  
4.   
5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
6.   
7. xsi:schemaLocation="http://www.springframework.org/schema/beans  
8.   
9. >  
10.   
11. <!-- 电脑bean -->  
12.   
13. <bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">  
14. <property name="name" value="HP6325笔记本" />  
15. </bean>  
16.   
17. <!-- 部门bean -->  
18.   
19. <bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">  
20. <property name="name" value="CSDN教育事业部" />  
21. </bean>  
22.   
23. <!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->  
24. <bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"  
25. autowire="constructor">  
26. </bean>  
27.   
28. </beans>

说明:

1、当构造器的参数类型在容器中找不全时。

比如：

CumpterBean时

1. <?xml version="1.0" encoding="UTF-8"?>  
2.   
3. <beans xmlns="http://www.springframework.org/schema/beans"  
4.   
5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
6.   
7. xsi:schemaLocation="http://www.springframework.org/schema/beans  
8.   
9. >  
10.   
11. <!-- 电脑bean -->  
12.   
13. <bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">  
14.   
15. <property name="name" value="HP6325笔记本" />  
16.   
17. </bean>  
18.   
19. <!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->  
20.   
21. <bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"  
22.   
23. autowire="constructor">  
24.   
25. </bean>  
26.   
27. </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：

1. <?xml version="1.0" encoding="UTF-8"?>  
2.   
3. <beans xmlns="http://www.springframework.org/schema/beans"  
4.   
5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
6.   
7. xsi:schemaLocation="http://www.springframework.org/schema/beans  
8.   
9. >  
10.   
11. <!-- 电脑bean -->  
12.   
13. <bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">  
14.   
15. <property name="name" value="HP6325笔记本" />  
16.   
17. </bean>  
18.   
19. <!-- 部门bean -->  
20.   
21. <bean id="deptBean" class="www.csdn.spring.autowire.bean.DeptBean">  
22.   
23. <property name="name" value="CSDN教育事业部" />  
24.   
25. </bean>  
26.   
27. <!-- 部门bean -->  
28.   
29. <bean id="deptBean1" class="www.csdn.spring.autowire.bean.DeptBean">  
30.   
31. <property name="name" value="CSDN教育事业部" />  
32.   
33. </bean>  
34.   
35.   
36. <!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->  
37.   
38. <bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"  
39.   
40. autowire="constructor">  
41.   
42. </bean>  
43.   
44. </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：

1. <?xml version="1.0" encoding="UTF-8"?>  
2.   
3. <beans xmlns="http://www.springframework.org/schema/beans"  
4.   
5. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
6.   
7. xsi:schemaLocation="http://www.springframework.org/schema/beans  
8.   
9. >  
10.   
11. <!-- 电脑bean -->  
12.   
13. <bean id="cumputerBean" class="www.csdn.spring.autowire.bean.CumputerBean">  
14.   
15. <property name="name" value="HP6325笔记本" />  
16.   
17. </bean>  
18.   
19. <!-- 部门bean -->  
20.   
21. <bean id="deptBean1" class="www.csdn.spring.autowire.bean.DeptBean">  
22.   
23. <property name="name" value="CSDN教育事业部" />  
24.   
25. </bean>  
26.   
27. <!-- 部门bean -->  
28.   
29. <bean id="deptBean2" class="www.csdn.spring.autowire.bean.DeptBean">  
30.   
31. <property name="name" value="CSDN教育事业部" />  
32.   
33. </bean>  
34.   
35. <!-- 员工bean 根据EmployeeBean中的 属性名称 bytype 去匹配 -->  
36.   
37. <bean id="employeeBean" class="www.csdn.spring.autowire.bean.EmployeeBean"  
38.   
39. autowire="constructor">  
40.   
41. </bean>  
42.   
43. </beans>

会出现如下bug（与byType的bug一致）:

1. org.springframework.beans.factory.UnsatisfiedDependencyException:   
2.   
3. Error creating bean with name 'employeeBean' defined in class path resource [spring-constructors.xml]:

1. Unsatisfied dependency expressed through constructor argument with index 0 of type [www.csdn.spring.autowire.bean.DeptBean]: :   
2.   
3. No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] is defined:   
4.   
5. expected single matching bean but found 2: deptBean1,deptBean2;   
6.   
7. nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException:  
8.   
9.  No qualifying bean of type [www.csdn.spring.autowire.bean.DeptBean] is defined:

1. expected single matching bean but found 2: deptBean1,deptBean2  
2.