I've a legacy system where query parameters are used to determine the class/method for a request using a simple in-house framework. E.g.
/endpoint?product=foo&action=bar&amount=1.0
/endpoint?product=foo&action=baz&amount=1.0
And I'd like map all actions for a product to one class so the plumbing can be greatly simplified, e.g.
#Controller
#RequestMapping("/endpoint/foo/**")
public class FooController {
#AutoWire
private FooProductService s; // one of many beans that have to be wired into lots of classes
#RequestMapping("/bar")
public void bar(#PathVariable String amount, Model model) {
// implementation omitted
}
#RequestMapping("/baz")
public void baz(#PathVariable String amount, Model model) {
// implementation omitted
}
}
It's a published API so we can't change the public API -> the URLs cannot change.
I thought that perhaps this could be done using configuration, as aspect or even a custom framework with out own annotations.
I believe you can do something like this for product=foo&action=bar&amount=1.0
#RequestMapping(value = "product={productName}&action={someaction}&amount={value}", method=RequestMethod.GET)
something(#PathVariable String productName, #PathVariable String someaction, #PathVariable String value)
if(someaction.equals("bar")) {
//do bar
}
if(someaction.equals("baz")) {
//do baz
}
}
HTH
Related
In the code below there are two methods annotated with #GetMapping annotation, one expects empty path, another one expects a path variable.
#Controller
#RequestMapping("/")
public class BasicController {
#GetMapping()
public String get(Model model) {
// doing something
}
#GetMapping("/{variable}")
public String getWithPathVar(#PathVariable("variable") String variable, Model model) {
// doing something different
}
}
Problem: When the app is running and I hit "www.myurl.com/" it enters both methods even though there is no path parameter. How can I fix this?
If so it sounds like a bug or some misconfiguration with filters. I can't reproduce this behaviour on the Spring 5.2.7. Here's an article that explains how Spring works under the hood.
If you can't upgrade the Spring version you can use only single endpoint as a workaround.
#GetMapping("/{variable}")
public String getWithPathVar(#PathVariable("variable") String variable, Model model) {
// doing something different
if(variable != null) {
// fulfill the normal workflow
} else {
// call ex get() workflow
}
}
I have a REST API built with Spring Boot / Spring MVC, using the implicit JSON serialization via Jackson.
Now, just before the implicit serialization, I would like to "inject" some UI texts from message resources into the objects that Jackson converts into JSON. Is there some neat, simple way to do this?
As a much simplified example, below I'd like to set Section title to a user-visible value, based purely based on its SectionType.
(Sure, I could hardcode the UI texts in SectionType, but I'd rather keep them separate, in resource files, because it's cleaner, and they might be localised at some point. And I can't autowire MessageSource in the entities / model objects which are not Spring-managed.)
#Entity
public class Entry {
// persistent fields omitted
#JsonProperty
public List<Sections> getSections() {
// Sections created on-the-fly, based on persistent data
}
}
public class Section {
public SectionType type;
public String title; // user-readable text whose value only depends on type
}
public enum SectionType {
MAIN,
FOO,
BAR;
public String getUiTextKey() {
return String.format("section.%s", name());
}
}
Somewhere in a #RestController:
#RequestMapping(value = "/entry/{id}", method = RequestMethod.GET)
public Entry entry(#PathVariable("id") Long id) {
return service.findEntry(id);
}
UI texts that I'd like to keep separate from code (messages_en.properties):
section.MAIN=Main Section
section.FOO=Proper UI text for the FOO section
section.BAR=This might get localised one day, you know
And what I'd like to do in a Spring-managed service/bean somewhere (using Messages, a very simple helper wrapping a MessageSource):
section.title = messages.get(section.type.getUiTextKey())
Note that if I call entry.getSections() and set the title for each, it will not affect the JSON output, since the Sections are generated on the fly in getSections().
Do I have to go all the way to custom deseriazation, or is there a simpler way to hook into the model objects just before they get serialized by Jackson?
Sorry if the question is unclear; I can try to clarify if needed.
As I said in the comment you can write an Aspect around every controller method that returns Section.
I wrote a simple example. You have to modify it with the message source.
Controller:
#RestController
#RequestMapping("/home")
public class HomeController {
#RequestMapping("/index")
public Person index(){
Person person = new Person();
person.setName("evgeni");
return person;
}
}
Aspect
#Aspect
#Component
public class MyAspect {
#Around("execution(public Person com.example..*Controller.*(..))")//you can play with the pointcut here
public Object addSectionMessage(ProceedingJoinPoint pjp) throws Throwable {
Object retVal = pjp.proceed();
Person p = (Person) retVal; // here cast to your class(Section) instead of Person
p.setAge(26);//modify the object as you wish and return it
return p;
}
}
Since the aspect is also a #Component you can #Autowire in it.
I want to pass some variables to my server. I did it this way, like shown in the example:
#Controller
#RequestMapping("/owners/{ownerId}")
public class RelativePathUriTemplateController {
#RequestMapping("/pets/{petId}")
public void findPet(#PathVariable String ownerId, #PathVariable String petId, Model model) {
// implementation omitted
}
}
This works totally fine when I send a request like this:
domain/owners/123/pets/123
But what I want to do is getting all pets of one owner. This means I dont need/want to pass a pet-ID:
domain/owners/123/pets/
But then I get an Excpetion that there is no Handler for this request. Is it possible to send a request like this or is it limited by Spring?
You have to add a second method:
#RequestMapping("/pets/")
public void findPetByOwner(#PathVariable String ownerId Model model) {
// implementation omitted
}
I have many controllers in my Spring MVC web application and there is a param mandatoryParam let's say which has to be present in all the requests to the web application.
Now I want to make that param-value available to all the methods in my web-layer and service-layer. How can I handle this scenario effectively?
Currently I am handling it in this way:
... controllerMethod(#RequestParam String mandatoryParam, ...)
and, then passing this param to service layer by calling it's method
#ControllerAdvice("net.myproject.mypackage")
public class MyControllerAdvice {
#ModelAttribute
public void myMethod(#RequestParam String mandatoryParam) {
// Use your mandatoryParam
}
}
myMethod() will be called for every request to any controller in the net.myproject.mypackage package. (Before Spring 4.0, you could not define a package. #ControllerAdvice applied to all controllers).
See the Spring Reference for more details on #ModelAttribute methods.
Thanks Alexey for leading the way.
His solution is:
Add a #ControllerAdvice triggering for all controllers, or selected ones
This #ControllerAdvice has a #PathVariable (for a "/path/{variable}" URL) or a #RequestParam (for a "?variable=..." in URL) to get the ID from the request (worth mentioning both annotations to avoid blind-"copy/past bug", true story ;-) )
This #ControllerAdvice then populates a model attribute with the data fetched from database (for instance)
The controllers with uses #ModelAttribute as method parameters to retrieve the data from the current request's model
I'd like to add a warning and a more complete example:
Warning: see JavaDoc for ModelAttribute.name() if no name is provided to the #ModelAttribute annotation (better to not clutter the code):
The default model attribute name is inferred from the declared
attribute type (i.e. the method parameter type or method return type),
based on the non-qualified class name:
e.g. "orderAddress" for class "mypackage.OrderAddress",
or "orderAddressList" for "List<mypackage.OrderAddress>".
The complete example:
#ControllerAdvice
public class ParentInjector {
#ModelAttribute
public void injectParent(#PathVariable long parentId, Model model) {
model.addAttribute("parentDTO", new ParentDTO(parentId, "A faked parent"));
}
}
#RestController
#RequestMapping("/api/parents/{parentId:[0-9]+}/childs")
public class ChildResource {
#GetMapping("/{childId:[0-9]+}")
public ChildDTO getOne(#ModelAttribute ParentDTO parent, long childId) {
return new ChildDTO(parent, childId, "A faked child");
}
}
To continue about the warning, requests are declaring the parameter "#ModelAttribute ParentDTO parent": the name of the model attribute is not the variable name ("parent"), nor the original "parentId", but the classname with first letter lowerified: "parentDTO", so we have to be careful to use model.addAttribute("parentDTO"...)
Edit: a simpler, less-error-prone, and more complete example:
#Target(ElementType.TYPE)
#Retention(RetentionPolicy.RUNTIME)
#Documented
#RestController
public #interface ProjectDependantRestController {
/**
* The value may indicate a suggestion for a logical component name,
* to be turned into a Spring bean in case of an autodetected component.
*
* #return the suggested component name, if any
*/
String value() default "";
}
#ControllerAdvice(annotations = ParentDependantRestController.class)
public class ParentInjector {
#ModelAttribute
public ParentDTO injectParent(#PathVariable long parentId) {
return new ParentDTO(parentId, "A faked parent");
}
}
#ParentDependantRestController
#RequestMapping("/api/parents/{parentId:[0-9]+}/childs")
public class ChildResource {
#GetMapping("/{childId:[0-9]+}")
public ChildDTO getOne(#ModelAttribute ParentDTO parent, long childId) {
return new ChildDTO(parent, childId, "A faked child");
}
}
I'm using Spring 4.0.0.RELEASE, Spring Data Commons 1.7.0.M1, Spring Hateoas 0.8.0.RELEASE
My resource is a simple POJO:
public class UserResource extends ResourceSupport { ... }
My resource assembler converts User objects to UserResource objects:
#Component
public class UserResourceAssembler extends ResourceAssemblerSupport<User, UserResource> {
public UserResourceAssembler() {
super(UserController.class, UserResource.class);
}
#Override
public UserResource toResource(User entity) {
// map User to UserResource
}
}
Inside my UserController I want to retrieve Page<User> from my service and then convert it to PagedResources<UserResource> using PagedResourcesAssembler, like displayed here: https://stackoverflow.com/a/16794740/1321564
#RequestMapping(value="", method=RequestMethod.GET)
PagedResources<UserResource> get(#PageableDefault Pageable p, PagedResourcesAssembler assembler) {
Page<User> u = service.get(p)
return assembler.toResource(u);
}
This doesn't call UserResourceAssembler and simply the contents of User are returned instead of my custom UserResource.
Returning a single resource works:
#Autowired
UserResourceAssembler assembler;
#RequestMapping(value="{id}", method=RequestMethod.GET)
UserResource getById(#PathVariable ObjectId id) throws NotFoundException {
return assembler.toResource(service.getById(id));
}
The PagedResourcesAssembler wants some generic argument, but then I can't use T toResource(T), because I don't want to convert my Page<User> to PagedResources<User>, especially because User is a POJO and no Resource.
So the question is: How does it work?
EDIT:
My WebMvcConfigurationSupport:
#Configuration
#ComponentScan
#EnableHypermediaSupport
public class WebMvcConfig extends WebMvcConfigurationSupport {
#Override
protected void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
argumentResolvers.add(pageableResolver());
argumentResolvers.add(sortResolver());
argumentResolvers.add(pagedResourcesAssemblerArgumentResolver());
}
#Bean
public HateoasPageableHandlerMethodArgumentResolver pageableResolver() {
return new HateoasPageableHandlerMethodArgumentResolver(sortResolver());
}
#Bean
public HateoasSortHandlerMethodArgumentResolver sortResolver() {
return new HateoasSortHandlerMethodArgumentResolver();
}
#Bean
public PagedResourcesAssembler<?> pagedResourcesAssembler() {
return new PagedResourcesAssembler<Object>(pageableResolver(), null);
}
#Bean
public PagedResourcesAssemblerArgumentResolver pagedResourcesAssemblerArgumentResolver() {
return new PagedResourcesAssemblerArgumentResolver(pageableResolver(), null);
}
/* ... */
}
SOLUTION:
#Autowired
UserResourceAssembler assembler;
#RequestMapping(value="", method=RequestMethod.GET)
PagedResources<UserResource> get(#PageableDefault Pageable p, PagedResourcesAssembler pagedAssembler) {
Page<User> u = service.get(p)
return pagedAssembler.toResource(u, assembler);
}
You seem to have already found out about the proper way to use but I'd like to go into some of the details here a bit for others to find as well. I went into similar detail about PagedResourceAssembler in this answer.
Representation models
Spring HATEOAS ships with a variety of base classes for representation models that make it easy to create representations equipped with links. There are three types of classes provided out of the box:
Resource - an item resource. Effectively to wrap around some DTO or entity that captures a single item and enriches it with links.
Resources - a collection resource, that can be a collection of somethings but usually are a collection of Resource instances.
PagedResources - an extension of Resources that captures additional pagination information like the number of total pages etc.
All of these classes derive from ResourceSupport, which is a basic container for Link instances.
Resource assemblers
A ResourceAssembler is now the mitigating component to convert your domain objects or DTOs into such resource instances. The important part here is, that it turns one source object into one target object.
So the PagedResourcesAssembler will take a Spring Data Page instance and transform it into a PagedResources instance by evaluating the Page and creating the necessary PageMetadata as well as the prev and next links to navigate the pages. By default - and this is probably the interesting part here - it will use a plain SimplePagedResourceAssembler (an inner class of PRA) to transform the individual elements of the page into nested Resource instances.
To allow to customize this, PRA has additional toResource(…) methods that take a delegate ResourceAssembler to process the individual items. So you end up with something like this:
class UserResource extends ResourceSupport { … }
class UserResourceAssembler extends ResourceAssemblerSupport<User, UserResource> { … }
And the client code now looking something like this:
PagedResourcesAssembler<User> parAssembler = … // obtain via DI
UserResourceAssembler userResourceAssembler = … // obtain via DI
Page<User> users = userRepository.findAll(new PageRequest(0, 10));
// Tell PAR to use the user assembler for individual items.
PagedResources<UserResource> pagedUserResource = parAssembler.toResource(
users, userResourceAssembler);
Outlook
As of the upcoming Spring Data Commons 1.7 RC1 (and Spring HATEOAS 0.9 transitively) the prev and next links will be generated as RFC6540 compliant URI templates to expose the pagination request parameters configured in the HandlerMethodArgumentResolvers for Pageable and Sort.
The configuration you've shown above can be simplified by annotating the config class with #EnableSpringDataWebSupport which would let you get rid off all the explicit bean declarations.
I wanted to convert list of Resources to page. but when giving it PagedResourcesAssembler it was eating up the internal links.
This will get your List paged.
public class JobExecutionInfoResource extends ResourceSupport {
private final JobExecutionInfo jobExecution;
public JobExecutionInfoResource(final JobExecutionInfo jobExecution) {
this.jobExecution = jobExecution;
add(ControllerLinkBuilder.linkTo(methodOn(JobsMonitorController.class).get(jobExecution.getId())).withSelfRel()); // add your own links.
}
public JobExecutionInfo getJobExecution() {
return jobExecution;
}
}
Paged resource Providing ResourceAssembler telling Paged resource to use it, which does nothing simply return's it back as it is already a resource list that is passed.
private final PagedResourcesAssembler<JobExecutionInfoResource> jobExecutionInfoResourcePagedResourcesAssembler;
public static final PageRequest DEFAULT_PAGE_REQUEST = new PageRequest(0, 20);
public static final ResourceAssembler<JobExecutionInfoResource, JobExecutionInfoResource> SIMPLE_ASSEMBLER = entity -> entity;
#GetMapping("/{clientCode}/{propertyCode}/summary")
public PagedResources<JobExecutionInfoResource> getJobsSummary(#PathVariable String clientCode, #PathVariable String propertyCode,
#RequestParam(required = false) String exitStatus,
#RequestParam(required = false) String jobName,
Pageable pageRequest) {
List<JobExecutionInfoResource> listOfResources = // your code to generate the list of resource;
int totalCount = 10// some code to get total count;
Link selfLink = linkTo(methodOn(JobsMonitorController.class).getJobsSummary(clientCode, propertyCode, exitStatus, jobName, DEFAULT_PAGE_REQUEST)).withSelfRel();
Page<JobExecutionInfoResource> page = new PageImpl<>(jobExecutions, pageRequest, totalCount);
return jobExecutionInfoResourcePagedResourcesAssembler.toResource(page, SIMPLE_ASSEMBLER, selfLink);
}
ALTERNATIVE WAY
Another way is use the Range HTTP header (read more in RFC 7233). You can define HTTP header this way:
Range: resources=20-41
That means, you want to get resource from 20 to 41 (including). This way allows consuments of API receive exactly defined resources.
It is just alternative way. Range is often used with another units (like bytes etc.)
RECOMMENDED WAY
If you wanna work with pagination and have really applicable API (hypermedia / HATEOAS included) then I recommend add Page and PageSize to your URL. Example:
http://host.loc/articles?Page=1&PageSize=20
Then, you can read this data in your BaseApiController and create some QueryFilter object in all your requests:
{
var requestHelper = new RequestHelper(Request);
int page = requestHelper.GetValueFromQueryString<int>("page");
int pageSize = requestHelper.GetValueFromQueryString<int>("pagesize");
var filter = new QueryFilter
{
Page = page != 0 ? page : DefaultPageNumber,
PageSize = pageSize != 0 ? pageSize : DefaultPageSize
};
return filter;
}
Your api should returns some special collection with information about number of items.
public class ApiCollection<T>
{
public ApiCollection()
{
Data = new List<T>();
}
public ApiCollection(int? totalItems, int? totalPages)
{
Data = new List<T>();
TotalItems = totalItems;
TotalPages = totalPages;
}
public IEnumerable<T> Data { get; set; }
public int? TotalItems { get; set; }
public int? TotalPages { get; set; }
}
Your model classes can inherit some class with pagination support:
public abstract class ApiEntity
{
public List<ApiLink> Links { get; set; }
}
public class ApiLink
{
public ApiLink(string rel, string href)
{
Rel = rel;
Href = href;
}
public string Href { get; set; }
public string Rel { get; set; }
}