Assume a Spring #RestController with a simple #GetMapping that accepts a VenueQuery dataclass as its parameter:
data class VenueQuery(
val cityId: Long? = null,
val countryIso: String? = null,
)
#RestController
open class VenueController {
#GetMapping("/venues")
open fun getVenues(
request: HttpServletRequest,
response: HttpServletResponse,
venueQuery: VenueQuery
) { ... }
}
Runing the code as above, works "well". GET /venues?cityId=1&countryIso=CZ gets deserialised into VenueQuery(cityId=1, countryIso="CZ"}.
However, annotating the venueQuery function argument with #RequestParam causes the same request to be rejected with BAD_REQUEST "Missing required parameter 'venueQuery'". This makes sense, but renders the former case even more confusing.
After searching for quite some time I still can't answer the following questions:
Where can I find a documentation that describes this behavior in more detail? I.e. any reference I could point to instead of relying on a one-time observation?
Is the first case even an expected behavior?
How does spring knows it should populate the venueQuery argument with query params, but not the request and response params? Does it infer by its types of servlet request/response?
Generally I struggle to find any documentation (not a "how to" but documentation) about how the Spring annotations and principles apply in Kotlin. Are there any notable sources?
Thanks for any answers!
Expected behavior?
Yes.
How does spring knows it should populate the venueQuery argument with query params?
By its type. Try two of VenueQuery and see what happens.
Generally I struggle to find any documentation...
Unless the behavior is markedly different, there’s no special mention for Kotlin. As for “notable sources”, I’ve always found the answers I’m looking for in their source code. Grab a cup of coffee and fire up a debugger, you’ll too.
Related
currently I'm exploring approaches to implement 'request timeout management in an AOP way in Spring Boot' with several restrictions. The requirements/restrictions are stated as below:
The original purpose is that if the processing time of an api request exceeds 5 seconds, then directly return timeout result instead of continue processing
The rest api to be monitored is implemented by standard spring mvc rest controller. All apis inside are returning json strings like this:
#RestController
public class xxxxxx {
#RequestMapping(value = "xxxxxxx")
public String xxxxxx(#RequestParam(value = "xxxx", required = true) String xxxx) {
....
return json.toString();
}
}
The timeout logic is required to be implemented by AOP
(The real mean part)
No changes should be made to the controllers, which means: Request generation approach should not be changed; Return type should not be changed(No 'Callable<...>' allowed)
I have already found 1 answer(Async approach) which can perfectly resolve the problem itself with spring async, and the timeout return result is very pretty, but it's changing the return type, and also touching the code in controller. I also found one solution(AOP approach) which is using AOP, but the scenario is quite different from mine. It's already moving some business logic into AOP class, but I'm not allowed to touch the controller code. I would be grateful if anyone can provide a solution. Solutions that can't meet all the restrictions but are minimizing the differences are also admitted.
Since there is still no response to this question, I will put my own temporary solution here.
I'm using Hystrix dependency.
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
<version>1.4.0.RELEASE</version>
</dependency>
It's well integrated with springboot, so the configuration is easy. Once properly configured, need to append an annotation on the request method that requires timeout handling. e.g.
#HystrixCommand(fallbackMethod="fallback")
#RequestMapping(value = "xxxxxxx")
public String xxxxxx(#RequestParam(value = "xxxx", required = true) String xxxx) {
....
return json.toString();
}
And need to add a fallback method with the name mapped to the value of 'fallbackMethod' inside annotation:
public String fallback() {
...
}
The timeout time value can be globally configured inside application.properties
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=3000
hystrix.command.default.circuitBreaker.sleepWindowInMilliseconds=3000
This is still not concise in these points:
Need to copy/paste this annotation for every method
Need to copy/paste the fallback method in every place hystrix is used
For hystrix fallback method itself, the parameter type and number need to be exactly same with the hystrix marked method. Currently I'm using several overloading method called 'fallback' for this, in each controller
But at least it's not changing method return types and code inside methods anymore and is the best solution I can think of currently. Will perform update once I find better solutions.
Most of my experience with creating controllers with Spring are for REST controllers that consume JSON formatted requests. I've been searching for documentation on how to do testing for form submission, and so far this is how I understand it should go using MockMvc:
MvcResult result = mockMvc.perform(post("/submit")
.param('title', 'test title')
.param('description', 'test description'))
.andReturn()
However, I'm not sure how to map the form parameters to a model object. I've seen the #ModelAttribute annotation pop up in my searches but I can't figure out how it should be used for mapping. In addition, this quick start guide from the official documentation does not elaborate on how things like th:object and th:field translate to HTML and subsequently to URL encoded form.
I have my controller code similar to the following:
#PostMapping('/submit')
def submit(#ModelAttribute WriteUp writeUp) {
//do something with writeUp object
'result'
}
I discovered through trial and error that my specific problem might have been Groovy specific. There test code and the controller code, it turns out, have no issues. To reiterate, for testing form submission, use the param method through perform method of MockMvcRequestBuilders. Another thing to note is that this doesn't seem to work if content type is not specified. Here's a sample test code that works for me:
MvcResult result = webApp.perform(post("/submit")
.contentType(APPLICATION_FORM_URLENCODED) //from MediaType
.param('title', 'test title')
.param('description', 'test description'))
.andReturn()
As you can see, it's not much different from what I posted originally. The controller code is pretty much just the same, with #ModelAttribute working just fine.
The problem with my setup though was that since I was using Groovy, I assumed that getters and setters were automatically generated in my WriteUp class. Here's how the WriteUp class looked originally:
class WriteUp {
private String title
private String description
}
I haven't written code in Groovy for a while, and the last time I did, classes like the one above can be assumed to have getters and setters implicitly. However, it turns out that is not the case. To solve my specific issue, I updated the access modifier in the fields to be default (package level):
class WriteUp {
String title
String description
}
I've seen the #ModelAttribute annotation pop up in my searches but I
can't figure out how it should be used for mapping.
When you mark your writeUp object with #ModelAttribute, then the Spring container populates the parameters (like title, description, etc..) from HttpServletRequest object & injects the object to the controller method, when the request comes to the server from the client (could be a Browser or MockMvc unit test client or anything else).
Also, few other basic points for your quick understanding:
(1) Controller methods are mapped to an URI and RequestMethod (like POST/GET/DELETE/PUT et..) like shown below:
#RequestMapping(value="/submit", method=RequestMethod.POST)
public String submit(#ModelAttribute WriteUp writeUp) {
//Call the service and Save the details
model.addAttribute("Writeup details added successfully");
return "writeUpResult"; //Returns to the View (JSP)
}
(2) #ModelAttribute will be mapped to an object (like your writeUp) for http POST/PUT requests where the html formd data is part of http body.
(3) #RequestParam or #PathParam will be used for http GET requests where the parameters are part of URL (i.e., not part of http body).
You can look here for understanding the DispatcherServlet request handling & Spring MVC basic web flow.
Scenario: I have a web application that uses Spring 3 MVC. Using the powerful new annotations in Spring 3 (#Controller, #ResponseBody etc), I have written some domain objects with #XML annotations for marhalling ajax calls to web clients. Everything works great. I declared my Controller class to have a return type #ResponseBody with root XML object - the payload gets marshalled correctly and sent to Client.
The problem is that some data in the content is breaking the XML compliance. I need to wrap this with CDATA when necessary. I saw a POST here How to generate CDATA block using JAXB? that recommends using a custom Content Handler. Ok, fantastic!
public class CDataContentHandler extends (SAXHandler|XMLSerializer|Other...) {
// see http://www.w3.org/TR/xml/#syntax
private static final Pattern XML_CHARS = Pattern.compile("[<>&]");
public void characters(char[] ch, int start, int length) throws SAXException {
boolean useCData = XML_CHARS.matcher(new String(c,start,length)).find();
if (useCData) super.startCDATA();
super.characters(ch, start, length);
if (useCData) super.endCDATA();
}
}
Using Spring MVC 3, how do I achieve this? Everything was "auto-magically" done for me with regards to the JAXB aspects of setup, Spring read the return type of the method, saw the annotations of the return type and picked up JAXB2 off the classpath to do the marshalling (Object to XML conversion). So where on earth is the "hook" that permits a user to register a custom Content Handler to the config?
Using EclipseLink JAXB implementation it is as easy as adding #XmlCDATA to the Object attribute concerned. Is there some smart way Spring can help out here / abstract this problem away into a minor configuration detail?
I know Spring isn't tied to any particular implementation but for the sake of this question, please can we assume I am using whatever the default implementation is. I tried the Docs here http://static.springsource.org/spring-ws/site/reference/html/oxm.html but it barely helped at all with this question from what I could understand.
Thanks all for any replies, be really appreciated.
Update:
Thanks for the suggested answer below Akshay. It was sufficient to put me on right tracks. Investigating further, I see there is a bit of history with this one between Spring version 3.05 and 3.2. In Spring 3.05 it used to be quite difficult to register a custom MessageConverter (this is really the goal here).
This conversation pretty much explains the thinking behind the development changes requested:
https://jira.springsource.org/browse/SPR-7504
Here is a link to the typically required class override to build a cusom solution:
http://static.springsource.org/spring/docs/3.1.0.M1/javadoc-api/org/springframework/http/converter/AbstractHttpMessageConverter.html
And the following Question on stack overflow is very similar to what I was asking for (except the #ResponseBody discussion relates to JSON and jackson) - the goal is basically the same.
Spring 3.2 and Jackson 2: add custom object mapper
So it looks like usage of , and overriding MarshallingHttpMessageConverter is needed, registering to AnnotationMethodHandlerAdapter. There is a recommended solution in link above to also get clever with this stuff and wrap the whole thing behind a custom defined Annotation.
I haven't yet developed a working solution but since I asked the questions, wanted to at least post something that may help others with the same sort of question, to get started. With all due respect, although this has all improved in Spring 3.2, it's still bit of a dogs dinner to get a little customization working... I really was expecting a one liner config change etc.
Rather than twist and bend Spring, perhaps the easiest answer for my particular issue is just to change JAXB2 implementation and use something like Eclipse Link JAXB that can do this out of the box.
Basically you need to create a custom HttpMessageConverter. Instead of relying on the Jaxb2RootElementHttpMessageConverter that spring uses by default.
Unfortunately, customizing one converter means you are telling spring that you will take care of loading all the converters you need! Which is fairly involved and can get complicated, based on whether you use annotations, component scanning, Spring 3.1 or earlier, etc.. The issue of how to add a custom converter is addressed here: Custom HttpMessageConverter with #ResponseBody to do Json things
In your custom message converter you are free to use any custom JAXB2 content handlers.
Another, simpler approach to solve your original problem would be to use a custom XmlJavaTypeAdapter. Create a custom implementation of javax.xml.bind.annotation.adapters.XmlAdapter to handle CDATA, in the marshal method wrap the return value with the cdata braces. Then in your mapped pojo, use the XmlAdapter annotation, pass it the class of your custom adapter and you should be done.
I have not myself implemented the adapter approach, so couldn't provide sample code. But it should work, and won't be a lot of work.
Hope this helps.
I am using Spring MVC for my web application.
I need to validate that the URL the user inputs is valid and was wondering if there is something in Spring that can do the basic checks for me (for example starts with http/https, has domain name etc).
ValidationUtils only contains very basic checks and I know I can write a regular expression in the validate() method however prefer to avoid it inm case someone has already done it :)
Thanks
In the past, I have always utilized Hibernate Validator. Simply annotate the appropriate field in your form bean with a #URL constraint.
If you've never used the ORM part of Hibernate before, don't let that scare you. The Validator portion is not dependent on the ORM stuff, and integrating it into Spring is very straightforward.
If for some reason you can't use Hibernate Validator... or you just want to stick with what you're comfortable with, a good place for regex's is RegExLib.com; several patterns that can match a URI are listed there.
Ended up using UrlValidator from apache commons.
I know this question is quite old, but I just need the same and I think I'll go with the PropertyEditors in SpringFramework.
More precisely there is URLEditor, which you can use to convert a String representation to an actual URL object.
Here is a link to the respective documentation:
http://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#beans-beans-conversion
http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/beans/propertyeditors/URLEditor.html
In my case, I think about using the following code within a Spring Validator to check whether a String entered by a user is a valid URL or not:
try {
PropertyEditor urlEditor = new URLEditor();
urlEditor.setAsText(field.getValue());
} catch (IllegalArgumentException ex) {
errors.rejectValue("nameOfTheFieldToBeValidated", "url_is_invalid");
}
However, as for now, I'm unsure whether it is possible to configure which protocol is going to be accepted as valid (i.e. URLEditor seems to also accept URLs starting with "classpath:")
Use a spring interceptor:
http://java.dzone.com/articles/using-spring-interceptors-your
Posted in spring forum with no response.
I have the following code snippet (from here), which is part of my pet project.
#Controller
#RequestMapping("/browse")
public class MediaBrowser {
...
#RequestMapping("/**")
public final ModelAndView listContents(final HttpServletRequest request) {
String folder = (String) request.getAttribute(
HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
...
}
I access the following url:
http://localhost:8080/myapp/browse
In spring 3.0.6.RELEASE, I got the folder variable as null, which is the expected value.
In spring 3.1.RC1, the folder variable is /browse.
Is this a bug or has something changed in spring-3.1?
As skaffman said, you probably shouldn't use PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE. Take a look at How to match a Spring #RequestMapping having a #pathVariable containing "/"? for an example of using AntPathMatcher to accomplish what you are trying
This looks very much like an internal implementation detail of the framework, one that you should not be relying on.
The javadoc for PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE says:
Note: This attribute is not required to be supported by all HandlerMapping implementations. URL-based HandlerMappings will typically support it, but handlers should not necessarily expect this request attribute to be present in all scenarios.
I wouldn't be surprised if the behaviour changed slightly between 3.0 and 3.1.