JSON parse error: Unexpected character (‘%‘ (code 37)): expected a valid value (number, String, arr

1 复现过程 POST  + @RequestBody + json格式的数据，不指定数据格式

MappingJackson2HttpMessageConverter 读取 application/x-www-form-urlencoded;charset=UTF-8 就会报异常：JSON parse error: Unexpected character ('%' (code 37)): expected a valid value (number, String, array, object, 'true', 'false' or 'null')

项目配置的参数转换器配置如下：指定MappingJackson2HttpMessageConverter 解析 application/x-www-form-urlencoded 数据

debug 可以定位到源码：

org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter#readJavaType
 
最终会调用com.fasterxml.jackson.databind.ObjectMapper#readValue(java.io.InputStream, com.fasterxml.jackson.databind.JavaType)
 
其中 InputStream 内容为 %7B%22keyWord%22%3A%22xx%22%2C%22offset%22%3A0%2C%22size%22%3A10%7D=
 
解码后是KV形式：{"keyWord":"xx","offset":0,"size":10}=

2 根本原因

POST请求传入了json格式的数据，但是却没有指定数据格式（默认） -H "Content-Type:application/x-www-form-urlencoded;charset=UTF-8"，引导jackson来解析kv格式的表单数据！

这就超级**了！ 正确做法是指定 content-type: application/json如下图（项目中指定MappingJackson2HttpMessageConverter 解析 application/x-www-form-urlencoded 数据）

3  GET 请求 + @RequestParam 

参数 curl -X GET '127.0.0.1:8080/add/employee?nameee=12&empId=0' 从注解中获取参数名如,KV

org.springframework.web.bind.annotation.RequestParam

4  GET 请求 + @RequestBody + 不指定content-type 也可以传输json数据

输入：curl -X GET --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list'
 
@RequestMapping(value = "/list", method = RequestMethod.GET)
public SearchRequest getHabitTitleMatchList(@RequestBody SearchRequest searchRequest,HttpServletRequest httpServletRequest) {
 
      return searchRequest;
 
}
 
输出：{"keyWord":"xx","offset":0,"size":10,"sort":0,"order":0}% 符合预期
 

   GET 不指定content-type 默认 application/x-www-form-urlencoded 

   先去根据表单---->如果没有--->再去找body（前提项目中指定MappingJackson2HttpMessageConverter 解析 application/x-www-form-urlencoded 数据 ）

匹配后还是用jackson可以解析http协议传输的data。如果指定content-type:application/json，当然更合理的顺利执行。

• 结论 ：对于GET请求只要，能匹配到MappingJackson2HttpMessageConverter 并且传输 data body为json格式就能，解析出符合预期的入参。

5  POST/GET 无 RequestBody注解并且非简单类型相当于给参数加了@ModelAttribut

A curl -X GET --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1111111'
 
{"keyWord":"1111111","offset":0,"size":100,"sort":0,"order":0}% 符合预期从表单找数据
 
B curl -X GET -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1111111'
 
// {"keyWord":"1111111","offset":0,"size":100,"sort":0,"order":0}% 符合预期 指定content-type 无效，依然从表单找数据
 
C curl -X POST -H 'content-type:application/json' '127.0.0.1:8080/list?keyWord=1233'
 
{"keyWord":"1233","offset":0,"size":100,"sort":0,"order":0}% 有/无@ModelAttribute 符合预期从表单找数据
 
D curl -X POST -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1233'
 
{"keyWord":"1233","offset":0,"size":100,"sort":0,"order":0}% 有/无@ModelAttribute 符合预期从表单找数据
 
E curl -X POST -H 'content-type:application/json' '127.0.0.1:8080/list?keyWord=1233'
 
{"keyWord":"1233","offset":0,"size":100,"sort":0,"order":0}% 无 @ModelAttribute 符合预期从表单找数据
 
解释：
 
(SearchRequest searchRequest)非简单类型 和@ModelAttribute 类似 方法签名决定了解析器-->ModelAttributeMethodProcessor
 
原因：construction---> Bean property binding and validation -->
 
org.springframework.web.method.annotation.ModelAttributeMethodProcessor#bindRequestParameters--->构造参数键值对
 
org.springframework.beans.MutablePropertyValues#MutablePropertyValues(java.util.Map)--->coyote 封装了请求参数

• 结论：GET请求参数直接使用@ModelAttribute 接受参数就OK了

6 POST/GET 有RequestBody注解 POST 必须指定 content-type:application/json

经由：
 
@RequestMapping(value = "/list", method = RequestMethod.POST/GET)
 
public SearchRequest getHabitTitleMatchList(@RequestBody SearchRequest searchRequest) {// RequestBody 方法签名决定了解析器jackson
 
return searchRequest;
 
}
 
A curl -X GET --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1111111'
 
// 无异常 但是不符合预期 {"keyWord":"1111111","offset":0,"size":100,"sort":0,"order":0}% GET提交表单-->提交解析url中参数异常（因为GET 先去根据表单---->如果没有--->再去找body）（前提 jackson 支持类型中有 application/x-www-form-urlencoded ）
 
B curl -X GET -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1111111'
 
// 无异常{"keyWord":"xx","offset":0,"size":10,"sort":0,"order":0}% GET 根据content直接去找body
 
C curl -X GET -H 'content-type:application/json' '127.0.0.1:8080/list?keyWord=1111111' 指定了content-type 必须要body（前提 jackson 支持类型中有 application/x-www-form-urlencoded ）
 
// Required request body is missing: public com.xiaodaka.rec.face.aspectj.SearchRequest
 
D curl -X GET --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list'
 
// 无异常 {"keyWord":"xx","offset":0,"size":10,"sort":0,"order":0}% GET 先去根据表单---->如果没有--->再去找body（前提 jackson 支持类型中有 application/x-www-form-urlencoded ）
 
curl -X POST -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1233' jackson-->解析body
 
// 无异常
 
curl -X POST --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1233'
 
// com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'keyWord' 表单-->提交解析url中参数异常
 
curl -X POST --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list'
 
// nested exception is com.fasterxml.jackson.core.JsonParseException: Unexpected character ('%' (code 37)) 表单-->skip(提交解析url中参数无)--->解析body异常

• 结论：一定要指定content-type 即使知道使用默认的content-type，GET 请求url不带参数但是带了body也是可以jackson解析的

7 其他情况列举

curl -X POST -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1233'
 
{"keyWord":"1233","offset":0,"size":100,"sort":0,"order":0}%
 
curl -X POST -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list'
 
{"keyWord":null,"offset":0,"size":100,"sort":0,"order":0}%
 
改为(@RequestBody SearchRequest searchRequest) 后：
 
curl -X POST -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list'
 
{"keyWord":"xx","offset":0,"size":10,"sort":0,"order":0}%
 
curl -X POST -H 'content-type:application/json' --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1233'
 
{"keyWord":"xx","offset":0,"size":10,"sort":0,"order":0}%
 
// 取消类型 application/x-www-form-urlencoded
 
curl -X POST --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1233'
 
{"timestamp":"2020-11-21","status":415,"error":"Unsupported Media Type","message":"Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported","path":"/list"}%
 
// 打开类型 application/x-www-form-urlencoded
 
curl -X POST --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list?keyWord=1233'
 
{"timestamp":"2020-11-21","status":400,"error":"Bad Request","message":"JSON parse error: Unrecognized token 'keyWord': was expecting ('true', 'false' or 'null'); nested exception is com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'keyWord': was expecting ('true', 'false' or 'null')\n at [Source: (ByteArrayInputStream); line: 1, column: 9]","path":"/list"}%
 
curl -X POST --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list' 但是（controller和curl method）改为GET就行了！！！
 
{"timestamp":"2020-11-21","status":400,"error":"Bad Request","message":"JSON parse error: Unexpected character ('%' (code 37)): expected a valid value (number, String, array, object, 'true', 'false' or 'null'); nested exception is com.fasterxml.jackson.core.JsonParseException: Unexpected character ('%' (code 37)): expected a valid value (number, String, array, object, 'true', 'false' or 'null')\n at [Source: (ByteArrayInputStream); line: 1, column: 2]","path":"/list"}%
 
curl -X GET --data '{"keyWord":"xx","offset":0,"size":10}' '127.0.0.1:8080/list'
 
{"keyWord":"xx","offset":0,"size":10,"sort":0,"order":0}% // 符合预期
 
GET 协议一起传输 POST 放到body中？？？ POST 必须指定content-type； GET 提交 --data数据不是body传输，但是可以用jackson解析