I'm developing a REST API backend with Spring for a Slack App. I was able to receive messages from Slack (the slash commands) but I'm not able to properly receive component interactions (button clicks).
The official documentation says:
Your Action URL will receive a HTTP POST request, including a payload body parameter, itself containing an application/x-www-form-urlencoded JSON string.
therefore I have written the following #RestController:
#RequestMapping(method = RequestMethod.POST, value = "/actions", headers = {"content-type=application/x-www-form-urlencoded"})
public ResponseEntity action(#RequestParam("payload") ActionController.Action action) {
return ResponseEntity.status(HttpStatus.OK).build();
}
#JsonIgnoreProperties(ignoreUnknown = true)
class Action {
#JsonProperty("type")
private String type;
public Action() {}
public String getType() {
return type;
}
}
however I get the following error:
Failed to convert request element: org.springframework.web.method.annotation.MethodArgumentConversionNotSupportedException: Failed to convert value of type 'java.lang.String' to required type 'controllers.ActionController$Action'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'controllers.ActionController$Action': no matching editors or conversion strategy found
What does it mean, and how to resolve?
You receive a string that contains a JSON content. You don't receive a JSON input as application/x-www-form-urlencoded is used as content type and not application/json as stated :
Your Action URL will receive a HTTP POST request, including a payload
body parameter, itself containing an application/x-www-form-urlencoded
JSON string.
So change the parameter type to String and use Jackson or any JSON library to map the String to your Action class :
#RequestMapping(method = RequestMethod.POST, value = "/actions", headers = {"content-type=application/x-www-form-urlencoded"})
public ResponseEntity action(#RequestParam("payload") String actionJSON) {
Action action = objectMapper.readValue(actionJSON, Action.class);
return ResponseEntity.status(HttpStatus.OK).build();
}
As pvpkiran suggests, you could have replaced #RequestParam by #RequestBody if you could pass the JSON string directly in the body of the POST request, and not as a value of a parameter but it seems that is not the case there.
Indeed by using #RequestBody, the body of the request is passed through an HttpMessageConverter to resolve the method argument.
To answer to your comment, Spring MVC doesn't provide a very simple way to achieve your requirement : mapping the String JSON to your Action class.
But if you really need to automatize this conversion you have a lengthy alternative as stated in the Spring MVC documentation such as Formatters (emphasis is mine) :
Some annotated controller method arguments that represent String-based
request input — e.g. #RequestParam, #RequestHeader, #PathVariable,
#MatrixVariable, and #CookieValue, may require type conversion if the
argument is declared as something other than String.
For such cases type conversion is automatically applied based on the
configured converters. By default simple types such as int, long,
Date, etc. are supported. Type conversion can be customized through a
WebDataBinder, see DataBinder, or by registering Formatters with the
FormattingConversionService, see Spring Field Formatting.
By creating a formatter (FormatterRegistry subclass) for your Action class you could add that in the Spring web config as documented :
#Configuration
#EnableWebMvc
public class WebConfig implements WebMvcConfigurer {
#Override
public void addFormatters(FormatterRegistry registry) {
// ... add action formatter here
}
}
and use it in your parameter declaration :
public ResponseEntity action(#RequestParam("payload") #Action Action actionJ)
{...}
For simplicity, you could use the code block below. #Request body maps the the payload to the Action class. It also validates to make sure that the type is not blank. The #Valid and #NotBlank is from javax.validation package.
#PostMapping("actions")
public ResponseEntity<?> startApplication(#RequestBody #Valid Action payload) {
// use your payload here
return ResponseEntity.ok('done');
}
class Action {
#NotBlank
private String type;
public Action() {
}
public String getType() {
return type;
}
}
Related
I need to upload from Post request MultipartFile and map a class from json.
My controller code looks like this:
#PostMapping(value = API_FILE_DIRECT_ENDPOINT,
consumes = {MediaType.MULTIPART_FORM_DATA_VALUE, MediaType.APPLICATION_JSON_VALUE }, produces = MediaType.APPLICATION_JSON_VALUE)
FileDto create( #RequestParam("file") #NotNull MultipartFile multipartFile,
#PathVariable( IbsAttachmentServiceApi.FILE_TYPE_KEY) String type,
#RequestParam("dto") #NotNull ApplyingFileDto applyingFileDto){
FileDto result= process(applyingFileDto, multipartFile);
return result;
}
when I'm trying to query it from Postman, like this
but it gives me an error
"Failed to convert value of type 'java.lang.String' to required type 'com.domain.ibs.attachment.model.ApplyingFileDto'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String' to required type 'com.domain.ibs.attachment.model.ApplyingFileDto': no matching editors or conversion strategy found"
So it doesn't map ApplyingFileDto class, only if I change it to String, and convert by ObjectMapper explicitly, then it works
#RequestParam("dto") #NotNull String applyingFileDto) ...
ApplyingFileDto mappedDto = objectMapper.readValue(applyingFileDto, ApplyingFileDto.class);
Is there is any way to configure editor to map it after #RequestParam ?
like the error says. You're trying to convert a String value to an ApplyingFileDto Object. The following method to pass objects to a service is to use the #RequestBody annotation.
I think that should solve your problem. Give it a try.
It can be because you are unnecessarily including #RequestParam in the controller method. You should use #RequestBody
But before that, Make sure the attributes received as request parameters have perfect getters and setters (eg for attribute bot - setBot) on the object to be mapped.
Add the object as a parameter in the controller method, but do not annotate with #RequestParam. The setter method of the target object will be called for each matching request parameter.
Example -
#PostMapping()
FileDto create(#RequestBody DTO dto) {
}
You have #RequestParam but the dto was not in your params it was in the body tab
I've found the solution for the answer. It is needed to add #RequestPart annotation instead #RequestParam like this
#PostMapping(value = API_FILE_DIRECT_ENDPOINT,
consumes = {MediaType.MULTIPART_FORM_DATA_VALUE, MediaType.APPLICATION_JSON_VALUE }, produces = MediaType.APPLICATION_JSON_VALUE)
FileDto create( #RequestParam("file") #NotNull MultipartFile multipartFile,
#PathVariable( IbsAttachmentServiceApi.FILE_TYPE_KEY) String type,
#RequestPart("dto") #NotNull ApplyingFileDto applyingFileDto){
FileDto result= process(applyingFileDto, multipartFile);
return result;
}
then reason for is in different type of converters.
It is mentioned here
Note that #RequestParam annotation can also be used to associate the
part of a "multipart/form-data" request with a method argument
supporting the same method argument types. The main difference is that
when the method argument is not a String or raw MultipartFile / Part,
#RequestParam relies on type conversion via a registered Converter or
PropertyEditor while RequestPart relies on HttpMessageConverters
taking into consideration the 'Content-Type' header of the request
part. RequestParam is likely to be used with name-value form fields
while RequestPart is likely to be used with parts containing more
complex content e.g. JSON, XML).
also this example is very useful
I am trying to give an enum value as a header parameter to my rest endpoint in a spring boot #RestController. To that end I put the jackson libraries in my build.gradle file since the autogenerated enum used jackson annotations. I cannot change the enum code (it is autogenerated from a openapi specification). It looks like this:
public enum DocumentTypes {
APPLICATION_PDF("application/pdf"),
APPLICATION_RTF("application/rtf"),
APPLICATION_VND_OASIS_OPENDOCUMENT_TEXT("application/vnd.oasis.opendocument.text"),
APPLICATION_VND_OPENXMLFORMATS_OFFICEDOCUMENT_WORDPROCESSINGML_DOCUMENT("application/vnd.openxmlformats-officedocument.wordprocessingml.document"),
APPLICATION_VND_MS_WORD("application/vnd.ms-word"),
TEXT_HTML("text/html"),
TEXT_PLAIN("text/plain");
private String value;
DocumentTypes(String value) {
this.value = value;
}
#Override
#JsonValue
public String toString() {
return String.valueOf(value);
}
#JsonCreator
public static DocumentTypes fromValue(String text) {
for (DocumentTypes b : DocumentTypes.values()) {
if (String.valueOf(b.value).equals(text)) {
return b;
}
}
throw new IllegalArgumentException("Unexpected value '" + text + "'");
}
}
The restcontroller I am using to test looks like this:
#RestController
#RequestMapping("/test")
public class TestController {
#Autowired
private ObjectMapper objectMapper;
#RequestMapping(path = "", method = RequestMethod.GET)
public void test(#RequestHeader(value = "Accept", required = false) DocumentTypes targetFormat) throws IOException {
DocumentTypes value = objectMapper.readValue("\"application/pdf\"", DocumentTypes.class);
}
}
If I don't supply the Accept header and just let break inside the code I can see that the first line of the code works fine, the application/pdf String is transformed into value so the ObjectMapper did its job using the #JsonCreator method.
However if I pass Accept=application/pdf header along with the request I get an error:
Failed to convert value of type 'java.lang.String' to required type 'de.some.namespace.model.DocumentTypes';
nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [#org.springframework.web.bind.annotation.RequestHeader de.some.namespace.model.DocumentTypes] for value 'application/pdf';
nested exception is java.lang.IllegalArgumentException: No enum constant de.some.namespace.model.DocumentTypes.application/pdf"
This looks to me as if spring is not using the Jackson provided ObjectMapper, thus ignoring the #JsonCreator method and just trying to resolve the enum by default by looking if there is a key with that provided name.
This to me does not make sense, becuase I also only #Autowire the ObjectMapper,... isn't that the one that spring should also use, how can I force spring to use the correct one for parsing the arguments? I tried putting it into a #Configuration and making it a #Bean and #Primary with the same results.
I have a workaround by implementing a converter:
#Component
public class StringToDocumentTypesConverter implements Converter<String, DocumentTypes> {
#Autowired
private ObjectMapper mapper;
#Override
public DocumentTypes convert(String s) {
try {
return mapper.readValue(String.format("\"%s\"", s), DocumentTypes.class);
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
}
But I don't understand why this would be necessary, normally spring automatically puts arguments through the ObjectMapper.
I think this is working as designed. Spring only uses the Jackson ObjectMapper for conversion of message bodies (using a registered HttpMessageConverter, specifically the MappingJackson2HttpMessageConverter).
This is documented at https://docs.spring.io/spring/docs/current/spring-framework-reference/web.html#mvc-ann-typeconversion:
Some annotated controller method arguments that represent String-based request input (such as #RequestParam, #RequestHeader, #PathVariable, #MatrixVariable, and #CookieValue) can require type conversion if the argument is declared as something other than String.
For such cases, type conversion is automatically applied based on the configured converters
And https://docs.spring.io/spring/docs/current/spring-framework-reference/web.html#mvc-ann-requestbody:
You can use the #RequestBody annotation to have the request body read and deserialized into an Object through an HttpMessageConverter
I have a simple servlet as follows:
#RestController
public class TestServlet {
#RequestMapping(value = "/test1")
public String test1() {
return "test1";
}
#RequestMapping(value = "/test2")
public String test2(#RequestBody TestClass req) {
return "test2";
}
public static class TestClass {
private String value;
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
}
But only the servlet not receiving parameters is working:
Works: http://localhost:8080/test1
Doesn't work: http://localhost:8080/test2?value=1234
org.springframework.http.converter.HttpMessageNotReadableException:
Required request body is missing: public java.lang.String
Why is the #RequestBody annotation not working? Am I missing an important piece?
One of the differences between #Controller and #RestController is that you don't have to write #RequestBody and #ResponseBody, that means that any parameter in your controller method which does not have an annotation (like #PathVariable, #ModelAttribute, ...) will implicitly have #RequestBody, and must therefore be POSTed as the HTTP entity body. So you need to send JSON/XML as part of a POST. What you have done is to send data on as part of the URL, which makes it a request parameter and not body-data, and you need #RequestParam to to extract data from the URL.
Also, I would recommend that you use the #GetMapping/#PostMapping or include the method parameter in the #RequestMapping annotation, it is highly unlikely that you want a service to be used for both POST and GET, so you should be as specific as possible in you controller method descriptions, to limit error scenarios.
The reason the second URL does not work is because when using #RequestBody the data you are sending to the endpoint needs to come through via the data attribute in the request header. When you append ?attr=value to your URL that is sending the attribute in the params header.
There are two ways to fix this:
Change your endpoint to read something like this:
public String test2(#RequestParam("value") TestClass req) {
//Endpoint code
}
Change your endpoint to read something like this:
#RequestMapping(value="test2",method=RequestMethod.POST)
public String test2(#RequestBody TestClass req){
//Endpoint code
}
and make your call similar to this (e.g. angularjs):
http.post({url:/*url*/,data:/*object to send*/});
The second option will most likely be what you want to go with because it looks like you are trying to send a json object to your endpoint and I believe you can only do that by making a POST request rather than a GET request
Just leave out the #RequestBody annotation, as this is only for POST requests.
public String test2(#Valid TestClass req) {
return "test2";
}
When you declare a controller method parameter as #RequestBody, you are wishing it to be recovered from the request body and not as a "regular" http parameter.
You could try using any kind of plugin for Firefox (RESTClient) or Chrome (PostMan) and try using one of them. You could do it using SoapUI as well.
The request should be a POST to the requested url this way:
POST http://localhost:8080/test2
You must provide http headers provinding expected Content-Type and Accept. In case of using Json, set them like this:
Content-Type: application/json
Accept: text/html (As your method returns only a String)
And then write the param to the request body. If in Json, like this:
{
"value":"the provided value"
}
How come this code just works? I didn't specify any custom converter or annotation (like #RequestBody or #ModelAttribute) before argument ? Request is filled correctly from this GET call:
http://localhost:8080/WS/foo?token=C124EBD7-D9A5-4E21-9C0F-3402A1EE5E9B&lastSync=2001-01-01T00:00:00&pageNo=1
Code:
#RestController
#RequestMapping(value = "/foo")
public class FooController {
#RequestMapping(method = RequestMethod.GET)
public Result<Foo> excursions(Request request) {
// ...
}
}
Request is just POJO with getters and setters. I use it to shorten argument code because plenty methods uses those same arguments ...
public class Request {
private String token;
#DateTimeFormat(pattern = IsoDateTime.DATETIME)
private Date lastSync;
private Integer pageNo;
// getters and setters
}
This was my original method before introducing Request.
#RestController
#RequestMapping(value = "/foo")
public class FooController {
#RequestMapping(method = RequestMethod.GET)
public Result<Foo> excursions(#RequestParam String token, #RequestParam #DateTimeFormat(pattern = IsoDateTime.DATETIME) Date lastSync, #RequestParam Integer pageNo) {
// ...
}
}
Request parameters will be mapped to POJOs, as it is happening in your case, by default. Additionally, if you use #ModelAttribute, an attribute in the Model will be created. That attribute can be then used in views, e.g. JSPs, to access the object.
#RequestBody annotation tells that the body of the request is NOT a set of form parameters like
token=C124EBD7-D9A5-4E21-9C0F-3402A1EE5E9B&lastSync=2001-01-01T00:00:00&pageNo=1
but is in some other format, such as JSON.
This is a feature provided by Spring MVC:
Customizable binding and validation. Type mismatches as application-level validation errors that keep the offending value, localized date and number binding, and so on instead of String-only form objects with manual parsing and conversion to business objects.
You can see it in the doc: http://docs.spring.io/spring/docs/4.2.x/spring-framework-reference/htmlsingle/
My question is essentially a follow-up to this question.
#RestController
public class TestController
{
#RequestMapping("/getString")
public String getString()
{
return "Hello World";
}
}
In the above, Spring would add "Hello World" into the response body. How can I return a String as a JSON response? I understand that I could add quotes, but that feels more like a hack.
Please provide any examples to help explain this concept.
Note: I don't want this written straight to the HTTP Response body, I want to return the String in JSON format (I'm using my Controller
with RestyGWT which requires the response to be in valid JSON
format).
Either return text/plain (as in Return only string message from Spring MVC 3 Controller) OR wrap your String is some object
public class StringResponse {
private String response;
public StringResponse(String s) {
this.response = s;
}
// get/set omitted...
}
Set your response type to MediaType.APPLICATION_JSON_VALUE (= "application/json")
#RequestMapping(value = "/getString", method = RequestMethod.GET,
produces = MediaType.APPLICATION_JSON_VALUE)
and you'll have a JSON that looks like
{ "response" : "your string value" }
JSON is essentially a String in PHP or JAVA context. That means string which is valid JSON can be returned in response. Following should work.
#RequestMapping(value="/user/addUser", method=RequestMethod.POST)
#ResponseBody
public String addUser(#ModelAttribute("user") User user) {
if (user != null) {
logger.info("Inside addIssuer, adding: " + user.toString());
} else {
logger.info("Inside addIssuer...");
}
users.put(user.getUsername(), user);
return "{\"success\":1}";
}
This is okay for simple string response. But for complex JSON response you should use wrapper class as described by Shaun.
In one project we addressed this using JSONObject (maven dependency info). We chose this because we preferred returning a simple String rather than a wrapper object. An internal helper class could easily be used instead if you don't want to add a new dependency.
Example Usage:
#RestController
public class TestController
{
#RequestMapping("/getString")
public String getString()
{
return JSONObject.quote("Hello World");
}
}
You can easily return JSON with String in property response as following
#RestController
public class TestController {
#RequestMapping(value = "/getString", produces = MediaType.APPLICATION_JSON_VALUE)
public Map getString() {
return Collections.singletonMap("response", "Hello World");
}
}
Simply unregister the default StringHttpMessageConverter instance:
#Configuration
public class WebMvcConfiguration extends WebMvcConfigurationSupport {
/**
* Unregister the default {#link StringHttpMessageConverter} as we want Strings
* to be handled by the JSON converter.
*
* #param converters List of already configured converters
* #see WebMvcConfigurationSupport#addDefaultHttpMessageConverters(List)
*/
#Override
protected void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.removeIf(c -> c instanceof StringHttpMessageConverter);
}
}
Tested with both controller action handler methods and controller exception handlers:
#RequestMapping("/foo")
public String produceFoo() {
return "foo";
}
#ExceptionHandler(FooApiException.class)
public String fooException(HttpServletRequest request, Throwable e) {
return e.getMessage();
}
Final notes:
extendMessageConverters is available since Spring 4.1.3, if are running on a previous version you can implement the same technique using configureMessageConverters, it just takes a little bit more work.
This was one approach of many other possible approaches, if your application only ever returns JSON and no other content types, you are better off skipping the default converters and adding a single jackson converter. Another approach is to add the default converters but in different order so that the jackson converter is prior to the string one. This should allow controller action methods to dictate how they want String to be converted depending on the media type of the response.
I know that this question is old but i would like to contribute too:
The main difference between others responses is the hashmap return.
#GetMapping("...")
#ResponseBody
public Map<String, Object> endPointExample(...) {
Map<String, Object> rtn = new LinkedHashMap<>();
rtn.put("pic", image);
rtn.put("potato", "King Potato");
return rtn;
}
This will return:
{"pic":"a17fefab83517fb...beb8ac5a2ae8f0449","potato":"King Potato"}
Make simple:
#GetMapping("/health")
public ResponseEntity<String> healthCheck() {
LOG.info("REST request health check");
return new ResponseEntity<>("{\"status\" : \"UP\"}", HttpStatus.OK);
}
Add produces = "application/json" in #RequestMapping annotation like:
#RequestMapping(value = "api/login", method = RequestMethod.GET, produces = "application/json")
Hint: As a return value, i recommend to use ResponseEntity<List<T>> type. Because the produced data in JSON body need to be an array or an object according to its specifications, rather than a single simple string. It may causes problems sometimes (e.g. Observables in Angular2).
Difference:
returned String as json: "example"
returned List<String> as json: ["example"]
Add #ResponseBody annotation, which will write return data in output stream.
This issue has driven me mad: Spring is such a potent tool and yet, such a simple thing as writing an output String as JSON seems impossible without ugly hacks.
My solution (in Kotlin) that I find the least intrusive and most transparent is to use a controller advice and check whether the request went to a particular set of endpoints (REST API typically since we most often want to return ALL answers from here as JSON and not make specializations in the frontend based on whether the returned data is a plain string ("Don't do JSON deserialization!") or something else ("Do JSON deserialization!")). The positive aspect of this is that the controller remains the same and without hacks.
The supports method makes sure that all requests that were handled by the StringHttpMessageConverter(e.g. the converter that handles the output of all controllers that return plain strings) are processed and in the beforeBodyWrite method, we control in which cases we want to interrupt and convert the output to JSON (and modify headers accordingly).
#ControllerAdvice
class StringToJsonAdvice(val ob: ObjectMapper) : ResponseBodyAdvice<Any?> {
override fun supports(returnType: MethodParameter, converterType: Class<out HttpMessageConverter<*>>): Boolean =
converterType === StringHttpMessageConverter::class.java
override fun beforeBodyWrite(
body: Any?,
returnType: MethodParameter,
selectedContentType: MediaType,
selectedConverterType: Class<out HttpMessageConverter<*>>,
request: ServerHttpRequest,
response: ServerHttpResponse
): Any? {
return if (request.uri.path.contains("api")) {
response.getHeaders().contentType = MediaType.APPLICATION_JSON
ob.writeValueAsString(body)
} else body
}
}
I hope in the future that we will get a simple annotation in which we can override which HttpMessageConverter should be used for the output.
Simple and Straightforward send any object or return simple List
#GetMapping("/response2")
#ResponseStatus(HttpStatus.CONFLICT)
#ResponseBody List<String> Response2() {
List<String> response = new ArrayList<>(Arrays.asList("Response2"));
return response;
}
I have added HttpStatus.CONFLICT as Random response to show how to pass RequestBody also the HttpStatus
Annotate your method with the #ResponseBody annotation to tell spring you are not trying to render a view and simple return the string plain