java - Spring mvc :annotation-driven 问题

Question

我有一个像这样的 Controller

@RequestMapping(value = {TABLE_URL}, method = RequestMethod.POST)
@ResponseBody
public TableModel checkAvailability(@ModelAttribute TableQueryForm TableQueryForm, 
        TableContext table, BindingResult bindingResult) throws Exception {
    // body
}

这里的 TableContext 是一个接口(interface)，它有一个实现并且工作正常。

最近我需要添加一个自定义日期格式化程序，所以在添加它以启用它之后我添加了行

<mvc:annotation-driven conversion-service="conversionService"/>

如前所述here

现在添加后，我的请求因以下异常而失败

Wrapped by: java.lang.IllegalStateException: No primary or default constructor found for interface com.table.domain.search.TableContext
    at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.createAttribute(ModelAttributeMethodProcessor.java:212)
    at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.createAttribute(ServletModelAttributeMethodProcessor.java:84)
    at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:132)
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:124)
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:161)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:131)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:877)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)

此类的实现没有定义构造函数，因此默认情况下应该激活默认构造函数。我不知道为什么会这样。请帮我解决这个问题。

Answer 1

如果不提供适当的 HandlerMethodArgumentResolver，则无法在 spring 处理程序中注入(inject)自定义 java 接口(interface).请注意“自定义”一词，因为 Spring 可以注入(inject)其他接口(interface)的实现，如 HttpServletRequest、HttpServletResponse、Reader、Writer 等。在这些情况下，Spring 会注入(inject)适当的具体实现。对于自定义 java 类(如果它只是接口(interface))，这不可能的原因可以从您得到的错误堆栈跟踪中看出。如果您的接口(interface)没有自定义处理程序解析器，则解析逻辑会回退到默认的 ModelAttributeMethodProcessor 上，它会尝试在所有情况下为所提到的接口(interface)类找到构造函数，但是由于在 java 中，接口(interface)不能有构造函数，因此失败(请注意带有 FAILS 的行这里)

public class ModelAttributeMethodProcessor {

protected Object createAttribute(String attributeName, MethodParameter parameter,
            WebDataBinderFactory binderFactory, NativeWebRequest webRequest) throws Exception {

        MethodParameter nestedParameter = parameter.nestedIfOptional();
        Class<?> clazz = nestedParameter.getNestedParameterType();

        Constructor<?> ctor = BeanUtils.findPrimaryConstructor(clazz);
        if (ctor == null) {
            Constructor<?>[] ctors = clazz.getConstructors();
            if (ctors.length == 1) {
                ctor = ctors[0];
            }
            else {
                try {
                    ctor = clazz.getDeclaredConstructor(); // FAILS HERE
                }
                catch (NoSuchMethodException ex) {
                    throw new IllegalStateException("No primary or default constructor found for " + clazz, ex);
                }
            }
        }
......................................
......................................

我尝试了以下测试类(class)

public interface TestInterface {    
    public void test() ;
}

@Component
public class TestInterfaceImpl implements TestInterface {

    @Override
    public void test() {
        System.out.println("Test called");      
    }

}

如果我的测试 Controller 是

 @RestController
    @RequestMapping("/test")
    public class TestController {   

        @GetMapping("test")
        public String withParam(TestInterface testInterface) {
            return "test";
        }

我遇到了和你一样的错误

Caused by: java.lang.IllegalStateException: No primary or default constructor found for interface com.shailendra.TestInterface
    at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.createAttribute(ModelAttributeMethodProcessor.java:212)
    at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.createAttribute(ServletModelAttributeMethodProcessor.java:84)
    at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:132)

但是如果我在下面使用

@RestController
@RequestMapping("/test")
public class TestController {   

    @GetMapping("test")
    public String withParam(TestInterfaceImpl test) {
        return "test";
    }

我得到了正确的回应。

如果接口(interface)注入(inject)有效，那么看起来你之前配置了一个合适的 HandlerMethodArgumentResolver，但不知何故，由于你的更改，现在它没有被拾取(可能是因为配置被排除在 spring 扫描之外)