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) {

但是当我尝试调用这个方法时，spring 抱怨:未能将java.lang.String"类型的值转换为所需类型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 注释似乎没有什么区别.

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

手动解析json有效，所以Jackson必须在classpath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?我是否正在尝试做一些不受支持的事情?

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

推荐答案

您的参数应该是 @RequestParam、或 @RequestBody>，两者都不是.

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

@RequestBody 用于 POST 和 PUT 请求，其中请求的正文是您要解析的内容.@RequestParam 用于命名参数，无论是在 URL 上还是作为多部分表单提交.

@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 的工作方式，它通常作为请求正文发送.

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 并查看是否有效.如果没有，并且您确实将 JSON 作为请求参数发布，那么如果没有额外的管道，Spring 将无法帮助您处理它(请参阅 自定义 WebDataBinder 初始化).

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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