Java 由于输入结束杰克逊解析器，没有要映射的内容
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No content to map due to end-of-input Hymanson parser
提问by Swapnil
I am getting this response from the server {"status":"true","msg":"success"}
我从服务器收到此响应 {"status":"true","msg":"success"}
I am trying to parse this json string using Hymanson parser library but somehow I am facing mapping-exception stating
我正在尝试使用 Hymanson 解析器库解析这个 json 字符串，但不知何故我正面临映射异常说明
com.fasterxml.Hymanson.databind.JsonMappingException: No content to map due to end-of-input
at [Source: java.io.StringReader@421ea4c0; line: 1, column: 1]
Why do we get this kind of exceptions?
为什么我们会遇到这种异常？
How to understand what is causing this exception?
如何理解导致此异常的原因？
I am trying to parse using following way:
我正在尝试使用以下方式解析：
StatusResponses loginValidator = null;
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(Feature.AUTO_CLOSE_SOURCE, true);
try {
String res = result.getResponseAsString();//{"status":"true","msg":"success"}
loginValidator = objectMapper.readValue(result.getResponseAsString(), StatusResponses.class);
} catch (Exception e) {
e.printStackTrace();
}
StatusResponse class
状态响应类
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({ "status","msg" })
public class StatusResponses {
@JsonProperty("status")
public String getStatus() {
return status;
}
@JsonProperty("status")
public void setStatus(String status) {
this.status = status;
}
@JsonProperty("msg")
public String getMessage() {
return message;
}
@JsonProperty("msg")
public void setMessage(String message) {
this.message = message;
}
@JsonProperty("status")
private String status;
@JsonProperty("msg")
private String message;
private Map<String, Object> additionalProperties = new HashMap<String, Object>();
@JsonGetter
public Map<String, Object> getAdditionalProperties() {
return additionalProperties;
}
@JsonSetter
public void setAdditionalProperties(Map<String, Object> additionalProperties) {
this.additionalProperties = additionalProperties;
}
}
采纳答案by Swapnil
import com.fasterxml.Hymanson.core.JsonParser.Feature;
import com.fasterxml.Hymanson.databind.ObjectMapper;
StatusResponses loginValidator = null;
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(Feature.AUTO_CLOSE_SOURCE, true);
try {
String res = result.getResponseAsString();//{"status":"true","msg":"success"}
loginValidator = objectMapper.readValue(res, StatusResponses.class);//replaced result.getResponseAsString() with res
} catch (Exception e) {
e.printStackTrace();
}
Don't know how it worked and why it worked? :( but it worked
不知道它是如何工作的以及它为什么工作？:(但它起作用了
回答by Katerina A.
For one, @JsonProperty("status")and @JsonProperty("msg")should only be there only when declaring the fields, not on the setters and geters.
首先，@JsonProperty("status")和@JsonProperty("msg")只能在声明字段时，不会对setter和geters在那里而已。
In fact, the simplest way to parse this would be
事实上，解析这个最简单的方法是
@JsonAutoDetect //if you don't want to have getters and setters for each JsonProperty
public class StatusResponses {
@JsonProperty("status")
private String status;
@JsonProperty("msg")
private String message;
}
回答by Amol
I could fix this error. In my case, the problem was at client side. By mistake I did not close the stream that I was writing to server. I closed stream and it worked fine. Even the error sounds like server was not able to identify the end-of-input.
我可以修复这个错误。就我而言，问题出在客户端。我错误地没有关闭我正在写入服务器的流。我关闭了流，它运行良好。即使错误听起来像服务器无法识别输入结束。
OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
out.write(jsonstring.getBytes());
out.close() ; //This is what I did
回答by jdolds
I had a similar error today and the issue was the content-type header of the post request. Make sure the content type is what you expect. In my case a "multipart/form-data" content-type header was being sent to the API instead of "application/json".
我今天遇到了类似的错误，问题是发布请求的内容类型标头。确保内容类型符合您的预期。在我的情况下，“multipart/form-data”内容类型标头被发送到 API 而不是“application/json”。
回答by Omar Abdel Bari
In my case I was reading the stream in a jersey RequestEventListener I created on the server side to log the request body prior to the request being processed. I then realized that this probably resulted in the subsequent read to yield no string (which is what is passed over when the business logic is run). I verified that to be the case.
在我的情况下，我正在读取我在服务器端创建的 jersey RequestEventListener 中的流，以在处理请求之前记录请求正文。然后我意识到这可能导致后续读取不产生字符串（这是运行业务逻辑时传递的内容）。我证实确实如此。
So if you are using streams to read the JSON string be careful of that.
因此，如果您使用流来读取 JSON 字符串，请注意这一点。
回答by Farrukh Najmi
In my case the problem was caused by my passing a null InputStream to the ObjectMapper.readValue call:
在我的情况下，问题是由于我将 null InputStream 传递给 ObjectMapper.readValue 调用引起的：
ObjectMapper objectMapper = ...
InputStream is = null; // The code here was returning null.
Foo foo = objectMapper.readValue(is, Foo.class)
I am guessing that this is the most common reason for this exception.
我猜这是此异常的最常见原因。
回答by Prakash Palnati
A simple fix could be Content-Type: application/json
一个简单的修复可能是 Content-Type: application/json
You are probably making a REST API call to get the response.
您可能正在调用 REST API 来获取响应。
Mostly you are not setting Content-Type: application/jsonwhen you the request.
Content-Type: application/x-www-form-urlencodedwill be chosen which might be causing this exception.
大多数情况下，您没有Content-Type: application/json在请求时进行设置 。
Content-Type: application/x-www-form-urlencoded将被选择，这可能会导致此异常。
回答by ?smail Yavuz
I know this is weird but when I changed GetMappingto PostMappingfor both client and server side the error disappeared.
我知道这是奇怪的，但是当我改变GetMapping到PostMapping为客户端和服务器端错误消失。
Both client and server are Spring boot projects.
客户端和服务器都是 Spring 启动项目。
