There was an unexpected error (type=Bad Request, status=400). Failed to convert value of type ‘java.

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发布于 2024-04-08 10:21:26

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发布于 2024-04-08 10:21:26

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问题解答：

有解决办法是看注解，我的情况是参数上没有带注解，原因是接口接收参数类型是int,

int类型默认值为0 不能传空

错误情况：

@RequestParam(name = “userId”, required = false, defaultValue = " ") userId: Int

正确情况：

`@RequestParam(name = "userId", required = false, defaultValue = "0") userId: Int	`

2022-08-05 10:14:54.157 [http-nio-8080-exec-5] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:845} - DispatcherServlet with name 'spring-servlet' processing GET request for [/index]
2022-08-05 10:14:54.161 [http-nio-8080-exec-5] [DEBUG]  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping {AbstractHandlerMethodMapping.java:297} - Looking up handler method for path /index
2022-08-05 10:14:54.161 [http-nio-8080-exec-5] [DEBUG]  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping {AbstractHandlerMethodMapping.java:302} - Returning handler method [public java.lang.String com.xiangshi.wzc.devloper.pc.modules.index.IndexController.index()]
2022-08-05 10:14:54.162 [http-nio-8080-exec-5] [DEBUG]  org.springframework.beans.factory.support.DefaultListableBeanFactory {AbstractBeanFactory.java:248} - Returning cached instance of singleton bean 'indexController'
2022-08-05 10:14:54.162 [http-nio-8080-exec-5] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:931} - Last-Modified value for [/index] is: -1
2022-08-05 10:14:54.163 [http-nio-8080-exec-5] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:1225} - Rendering view [org.springframework.web.servlet.view.JstlView: name 'index'; URL [/WEB-INF/views/index.jsp]] in DispatcherServlet with name 'spring-servlet'
2022-08-05 10:14:54.165 [http-nio-8080-exec-5] [DEBUG]  org.springframework.web.servlet.view.JstlView {InternalResourceView.java:166} - Forwarding to resource [/WEB-INF/views/index.jsp] in InternalResourceView 'index'
2022-08-05 10:14:54.330 [http-nio-8080-exec-5] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {FrameworkServlet.java:996} - Successfully completed request
2022-08-05 10:14:54.332 [http-nio-8080-exec-5] [DEBUG]  org.springframework.beans.factory.support.DefaultListableBeanFactory {AbstractBeanFactory.java:248} - Returning cached instance of singleton bean 'sqlSessionFactory'
2022-08-05 10:14:54.514 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:845} - DispatcherServlet with name 'spring-servlet' processing GET request for [/order/ExportAll]
2022-08-05 10:14:54.516 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping {AbstractHandlerMethodMapping.java:297} - Looking up handler method for path /order/ExportAll
2022-08-05 10:14:54.533 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping {AbstractHandlerMethodMapping.java:302} - Returning handler method [public org.springframework.web.servlet.ModelAndView com.xiangshi.wzc.basecore.web.controller.BaseControllerImpl.viewOne(java.lang.Long)]
2022-08-05 10:14:54.533 [http-nio-8080-exec-6] [DEBUG]  org.springframework.beans.factory.support.DefaultListableBeanFactory {AbstractBeanFactory.java:248} - Returning cached instance of singleton bean 'orderController'
2022-08-05 10:14:54.533 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:931} - Last-Modified value for [/order/ExportAll] is: -1
2022-08-05 10:14:54.538 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver {AbstractHandlerExceptionResolver.java:134} - Resolving exception from handler [public org.springframework.web.servlet.ModelAndView com.xiangshi.wzc.basecore.web.controller.BaseControllerImpl.viewOne(java.lang.Long)]: org.springframework.beans.TypeMismatchException: Failed to convert value of type [java.lang.String] to required type [java.lang.Long]; nested exception is java.lang.NumberFormatException: For input string: "ExportAll"
2022-08-05 10:14:54.538 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver {AbstractHandlerExceptionResolver.java:134} - Resolving exception from handler [public org.springframework.web.servlet.ModelAndView com.xiangshi.wzc.basecore.web.controller.BaseControllerImpl.viewOne(java.lang.Long)]: org.springframework.beans.TypeMismatchException: Failed to convert value of type [java.lang.String] to required type [java.lang.Long]; nested exception is java.lang.NumberFormatException: For input string: "ExportAll"
2022-08-05 10:14:54.539 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver {AbstractHandlerExceptionResolver.java:134} - Resolving exception from handler [public org.springframework.web.servlet.ModelAndView com.xiangshi.wzc.basecore.web.controller.BaseControllerImpl.viewOne(java.lang.Long)]: org.springframework.beans.TypeMismatchException: Failed to convert value of type [java.lang.String] to required type [java.lang.Long]; nested exception is java.lang.NumberFormatException: For input string: "ExportAll"
2022-08-05 10:14:54.539 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:1018} - Null ModelAndView returned to DispatcherServlet with name 'spring-servlet': assuming HandlerAdapter completed request handling
2022-08-05 10:14:54.539 [http-nio-8080-exec-6] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {FrameworkServlet.java:996} - Successfully completed request
2022-08-05 10:14:54.541 [http-nio-8080-exec-6] [DEBUG]  org.springframework.beans.factory.support.DefaultListableBeanFactory {AbstractBeanFactory.java:248} - Returning cached instance of singleton bean 'sqlSessionFactory'
2022-08-05 10:14:59.673 [http-nio-8080-exec-8] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:845} - DispatcherServlet with name 'spring-servlet' processing GET request for [/index]
2022-08-05 10:14:59.676 [http-nio-8080-exec-8] [DEBUG]  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping {AbstractHandlerMethodMapping.java:297} - Looking up handler method for path /index
2022-08-05 10:14:59.676 [http-nio-8080-exec-8] [DEBUG]  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping {AbstractHandlerMethodMapping.java:302} - Returning handler method [public java.lang.String com.xiangshi.wzc.devloper.pc.modules.index.IndexController.index()]
2022-08-05 10:14:59.676 [http-nio-8080-exec-8] [DEBUG]  org.springframework.beans.factory.support.DefaultListableBeanFactory {AbstractBeanFactory.java:248} - Returning cached instance of singleton bean 'indexController'
2022-08-05 10:14:59.677 [http-nio-8080-exec-8] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:931} - Last-Modified value for [/index] is: -1
2022-08-05 10:14:59.677 [http-nio-8080-exec-8] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {DispatcherServlet.java:1225} - Rendering view [org.springframework.web.servlet.view.JstlView: name 'index'; URL [/WEB-INF/views/index.jsp]] in DispatcherServlet with name 'spring-servlet'
2022-08-05 10:14:59.679 [http-nio-8080-exec-8] [DEBUG]  org.springframework.web.servlet.view.JstlView {InternalResourceView.java:166} - Forwarding to resource [/WEB-INF/views/index.jsp] in InternalResourceView 'index'
2022-08-05 10:14:59.840 [http-nio-8080-exec-8] [DEBUG]  org.springframework.web.servlet.DispatcherServlet {FrameworkServlet.java:996} - Successfully completed request
2022-08-05 10:14:59.843 [http-nio-8080-exec-8] [DEBUG]  org.springframework.beans.factory.support.DefaultListableBeanFactory {AbstractBeanFactory.java:248} - Returning cached instance of singleton bean 'sqlSessionFactory'

解决办法：

如果你是想这个参数必须传空的情况下。最简单的解决办法为将参数类型变成integer,代码中加校验如果为空怎么处理，不为空怎么处理。

不加校验会报错

当处理 Spring Framework 中的请求参数时，经常会涉及到使用 @RequestParam 注解来获取参数值并将其绑定到方法的参数上。然而，在设置参数类型、默认值以及处理参数为空的情况时，有一些关键点需要注意。

1. `@RequestParam` 注解简介

在 Spring Framework 中，@RequestParam 注解是一个常用的注解，用于从请求中获取参数的值。它可以应用于方法的参数上，将请求参数与方法参数进行绑定。在实际应用中，我们可能会遇到一些情况，需要对参数类型、默认值以及处理参数为空的情况进行特定的设置。

2. 参数类型与默认值设置

在使用 @RequestParam 注解时，参数类型和默认值的设置是十分重要的。考虑以下情况：

错误情况：

@RequestParam(name = "userId", required = false, defaultValue = " ") userId: Int

这里的错误在于将空格作为整数类型参数 userId 的默认值。实际上，defaultValue 应该设置为一个合法的整数值，以确保参数未提供时能够使用有效的默认值。

正确情况：

@RequestParam(name = "userId", required = false, defaultValue = "0") userId: Int

在这个正确的示例中，defaultValue 被设置为 "0"，这是一个合法的整数值。这样，当参数未提供时，userId 将使用默认值 0。

3. 处理参数为空的情况

对于需要处理参数为空的情况，您提出了一种解决方案，即将参数类型从 Int 更改为 Integer，并在代码中添加相应的校验。这是一个明智的做法，因为 Integer 类型可以接受 null 值，从而更好地处理参数值为空的情况。

例如，您可以使用如下方式来处理参数为空的情况：

@RequestMapping("/process")
public String processRequest(@RequestParam(name = "userId", required = false) userId: Integer) {
    if (userId == null) {
        // 处理参数为空的情况
    } else {
        // 处理参数不为空的情况
    }
    // ...
}

在这个例子中，我们使用了 Integer 类型的 userId 参数，并通过判断是否为 null 来处理参数为空和非空的情况。

4. 结论

处理 Spring Framework 中的请求参数时，正确设置参数类型、默认值，以及处理参数为空的情况，都是至关重要的。通过正确使用 @RequestParam 注解，您可以更好地控制参数的传递和处理，从而增强您的应用程序的可靠性和灵活性。同时，根据实际需要，您可以选择将参数类型设置为 Integer，以便更好地处理参数值为空的情况。这些技巧将有助于您在 Spring Framework 中有效地处理请求参数，提升代码质量和可维护性。

希望本篇博客对您理解和处理 Spring Framework 中的请求参数问题有所帮助。如果您有任何疑问或需要进一步的解释，请随时提问。

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原始发表：2023-08-11，如有侵权请联系 cloudcommunity@tencent.com 删除

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