Java Jackson JSON - 解组时“没有单字符串构造函数/工厂方法”错误
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Hymanson JSON - "no single-String constructor/factory method" error on unmarshal
提问by sat
The simplest of cases is causing me problems. I've run into it the first time. I am able to unmarshal slightly more complex json but this simple one fails.
最简单的情况给我带来了问题。我第一次遇到它。我能够解组稍微复杂的 json，但这个简单的失败了。
What would cause this and why is Hymanson having trouble with just a single string?
什么会导致这种情况，为什么Hyman逊只用一根弦就遇到问题？
A simple class holding the name of the user's role.
一个包含用户角色名称的简单类。
public class UpdateUserRole {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Inside the controller
控制器内部
public void updateUserRole(@PathVariable Long id, @RequestBody UpdateUserRoleReq req) {
}
As soon as Hymanson sees this, it throws this error
Hyman逊一看到这个，就会抛出这个错误
org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Can not instantiate value of type [simple type, class com.mycompany.UpdateUserRoleReq] from String value ('{"name":"admin_1407445357682"}'); no single-String constructor/factory method; nested exception is com.fasterxml.Hymanson.databind.JsonMappingException: Can not instantiate value of type [simple type, class com.mycompany.UpdateUserRoleReq] from String value ('{"name":"admin_1407445357682"}'); no single-String constructor/factory method
at org.springframework.http.converter.json.MappingHymanson2HttpMessageConverter.readJavaType(MappingHymanson2HttpMessageConverter.java:228)
at org.springframework.http.converter.json.MappingHymanson2HttpMessageConverter.read(MappingHymanson2HttpMessageConverter.java:220)
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:138)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:183)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:98)
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:79)
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:157)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:124)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
at org.springframework.web.servlet.FrameworkServlet.doPut(FrameworkServlet.java:874)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:649)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:110)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ApplicationContextFilterConfiguration.doFilterInternal(EndpointWebMvcAutoConfiguration.java:257)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
回答by Samuel Waggoner
I was able to solve a very similar problem by adhering exactly to the error message.
通过严格遵守错误消息，我能够解决一个非常相似的问题。
I added the equivalent in your case of a single-String constructor.
我在您的单字符串构造函数的情况下添加了等效项。
public class UpdateUserRole {
private String name;
public UpdateUserRole() {}
public UpdateUserRole(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
回答by Alvin Yue
I my case. I was sending in double escaped JSON string e.g. "{\"name\":\"abc\", \"age\":21}" and my String constructor only receive the JSON string completely. The other attributes (age) was not updated at all. Once I changed the input to {"name":"abc", "age":21}. Hymanson was able to automatically parse the JSON input into object(s).
我的情况。我正在发送双转义 JSON 字符串，例如 "{\"name\":\"abc\", \"age\":21}" 并且我的 String 构造函数只完全接收 JSON 字符串。其他属性（年龄）根本没有更新。一旦我将输入更改为 {"name":"abc", "age":21}。Hymanson 能够自动将 JSON 输入解析为对象。
回答by Mike
You have to add the construct method which contains single parameter. Just have a try.
您必须添加包含单个参数的构造方法。试试吧。
回答by dobrivoje
I folowed a Jira tutorial (https://developer.atlassian.com/server/jira/platform/oauth/) for OAuth. In my case, I used dto to json transformation with GSON lib, however I couldn't make it work. I'll provide source later, but for fast resolve, please see : https://stackoverflow.com/a/59981597/1551368
我遵循了OAuth的 Jira 教程（https://developer.atlassian.com/server/jira/platform/oauth/）。就我而言，我使用 dto 到 GSON lib 进行 json 转换，但是我无法使其工作。我稍后会提供源代码，但为了快速解决，请参阅：https: //stackoverflow.com/a/59981597/1551368
