在spring-mvc中将json解析为java对象

问题描述

我熟悉如何使用 @ResponseBody 注释从我的 @Controller 方法返回json。

I'm familiar with how to return json from my @Controller methods using the @ResponseBody annotation.

现在我正在尝试将一些json参数读入我的控制器，但到目前为止还没有运气。
这是我的控制器的签名：

Now I'm trying to read some json arguments into my controller, but haven't had luck so far.Here's my controller's signature:

@RequestMapping(value = "/ajax/search/sync")
public ModelAndView sync(@RequestParam("json") @RequestBody SearchRequest json) {

但是当我尝试调用此方法，spring抱怨：
无法将类型'java.lang.String'的值转换为必需类型'com.foo.SearchRequest'

But when I try to invoke this method, spring complains that:Failed to convert value of type 'java.lang.String' to required type 'com.foo.SearchRequest'

删除 @RequestBody 注释似乎没什么区别。

Removing the @RequestBody annotation doesn't seem to make a difference.

手动解析json是有效的，所以Jackson必须在类路径中：

Manually parsing the json works, so Jackson must be in the classpath:

// This works
@RequestMapping(value = "/ajax/search/sync")
public ModelAndView sync(@RequestParam("json") String json) {
    SearchRequest request;
    try {
        request = objectMapper.readValue(json, SearchRequest.class);
    } catch (IOException e) {
        throw new IllegalArgumentException("Couldn't parse json into a search request", e);
    }

有什么想法吗？我试图做一些不支持的事情吗？

Any ideas? Am I trying to do something that's not supported?

推荐答案

你的参数应该是 @RequestParam ，或 a @RequestBody ，而不是两者。

Your parameter should either be a @RequestParam, or a @RequestBody, not both.

@RequestBody 用于POST和PUT请求，其中请求的主体是您想要的解析。 @RequestParam 用于指定参数，可以是URL，也可以是多部分表单提交。

@RequestBody is for use with POST and PUT requests, where the body of the request is what you want to parse. @RequestParam is for named parameters, either on the URL or as a multipart form submission.

所以你需要决定你需要哪一个。你真的想把你的JSON作为请求参数吗？这通常不是AJAX的工作原理，它通常作为请求体发送。

So you need to decide which one you need. Do you really want to have your JSON as a request parameter? This isn't normally how AJAX works, it's normally sent as the request body.

尝试删除 @RequestParam 看看是否有效。如果没有，并且您真的将JSON作为请求参数发布，那么Spring将无法帮助您在没有额外管道的情况下处理它（请参阅）。

Try removing the @RequestParam and see if that works. If not, and you really are posting the JSON as a request parameter, then Spring won't help you process that without additional plumbing (see Customizing WebDataBinder initialization).

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