近期在捯饬spring的注解，现将遇到的问题记录下来，以供遇到同样问题的童鞋解决~

先说明下场景,代码如下：

有如下接口：

<pre>

public

interface

EmployeeService {

public

EmployeeDto getEmployeeById(Long id);
}

</pre>

同时有下述两个实现类 EmployeeServiceImpl和EmployeeServiceImpl1：

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<pre>

@Service("service")

public

class

EmployeeServiceImpl

implements

EmployeeService {

public

EmployeeDto getEmployeeById(Long id) {

return

new

EmployeeDto();
}
}

@Service("service1")

public

class

EmployeeServiceImpl1

implements

EmployeeService {

public

EmployeeDto getEmployeeById(Long id) {

return

new

EmployeeDto();
}
}

</pre>

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调用代码如下：

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<pre>

@Controller
@RequestMapping(

"/emplayee.do"

)

public

class

EmployeeInfoControl {

@Autowired

EmployeeService employeeService;

@RequestMapping(params

= "method=showEmplayeeInfo"

)

public

void

showEmplayeeInfo(HttpServletRequest request, HttpServletResponse response, EmployeeDto dto) {
#略
}
}

</pre>

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在启动tomcat时报如下错误：

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<pre>

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'employeeInfoControl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.test.service.EmployeeService com.test.controller.EmployeeInfoControl.employeeService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [com.test.service.EmployeeService] is defined: expected single matching bean but found 2: [service1, service2]

</pre>

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其实报错信息已经说得很明确了,在autoware时，由于有两个类实现了EmployeeService接口，所以Spring不知道应该绑定哪个实现类，所以抛出了如上错误。

这个时候就要用到@Qualifier注解了，qualifier的意思是合格者，通过这个标示，表明了哪个实现类才是我们所需要的，我们修改调用代码，添加@Qualifier注解，需要注意的是@Qualifier的参数名称必须为我们之前定义@Service注解的名称之一！

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<pre>

@Controller
@RequestMapping(

"/emplayee.do"

)

public

class

EmployeeInfoControl {

@Autowired
**@Qualifier(**

"service"

)
EmployeeService employeeService;

@RequestMapping(params

= "method=showEmplayeeInfo"

)

public

void

showEmplayeeInfo(HttpServletRequest request, HttpServletResponse response, EmployeeDto dto) {
#略
}
}

</pre>

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