wanting to use RestControllerAdvice and in like the default response from Spring have the path. Seems like via the ExceptionHandler I can use the WebRequest.
I can see the headers but unsure how to show the path. looked at the parameters but nothing in there showed the path. How can I obtain the path of the request:
#RestControllerAdvice
public class RestControllerExceptionHandler {
#Autowired
private ErrorAttributesConfig errAttrib;
#ExceptionHandler(value = {IOException.class})
#ResponseStatus(HttpStatus.BANDWIDTH_LIMIT_EXCEEDED)
public AppErrorAttributes internalServerError(Exception e, WebRequest h) {
System.out.println(h.getContextPath());
// for (Iterator<String> i = h.getParameterNames(); i.hasNext(); ) {
// System.out.println(i.next());
// }
String[] s = h.getAttributeNames(0);
for (Iterator<String> i = h.getHeaderNames(); i.hasNext();) {
System.out.println(i.next());
}
AppErrorAttributes aea = errAttrib.appErrorAttributes();
aea.setStatus(HttpStatus.BAD_REQUEST.value());
aea.setError(HttpStatus.BAD_REQUEST.getReasonPhrase());
aea.setMessage(e.getMessage());
return aea;
}
used
#ExceptionHandler(value = {IOException.class})
#ResponseStatus(HttpStatus.BANDWIDTH_LIMIT_EXCEEDED)
// public AppErrorAttributes internalServerError(Exception e, WebRequest h) {
public AppErrorAttributes internalServerError(Exception e, HttpServletRequest h) {
System.out.println(h.getServletPath());
System.out.println(h.getRequestURI());
Related
I'm trying to add custom tags - the path variables and their values from each request - to each metric micrometer generates. I'm using spring-boot with java 16.
From my research i've found that creating a bean of type WebMvcTagsContributor alows me to do just that.
This is the code
public class CustomWebMvcTagsContributor implements WebMvcTagsContributor {
private static int PRINT_ERROR_COUNTER = 0;
#Override
public Iterable<Tag> getTags(HttpServletRequest request, HttpServletResponse response,
Object handler,
Throwable exception) {
return Tags.of(getAllTags(request));
}
private static List<Tag> getAllTags(HttpServletRequest request) {
Object attributesMapObject = request.getAttribute(View.PATH_VARIABLES);
if (isNull(attributesMapObject)) {
attributesMapObject = request.getAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE);
if (isNull(attributesMapObject)) {
attributesMapObject = extractPathVariablesFromURI(request);
}
}
if (nonNull(attributesMapObject)) {
return getPathVariablesTags(attributesMapObject);
}
return List.of();
}
private static Object extractPathVariablesFromURI(HttpServletRequest request) {
Long currentUserId = SecurityUtils.getCurrentUserId().orElse(null);
try {
URI uri = new URI(request.getRequestURI());
String path = uri.getPath(); //get the path
UriTemplate uriTemplate = new UriTemplate((String) request.getAttribute(
HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE)); //create template
return uriTemplate.match(path); //extract values form template
} catch (Exception e) {
log.warn("[Error on 3rd attempt]", e);
}
return null;
}
private static List<Tag> getPathVariablesTags(Object attributesMapObject) {
try {
Long currentUserId = SecurityUtils.getCurrentUserId().orElse(null);
if (nonNull(attributesMapObject)) {
var attributesMap = (Map<String, Object>) attributesMapObject;
List<Tag> tags = attributesMap.entrySet().stream()
.map(stringObjectEntry -> Tag.of(stringObjectEntry.getKey(),
String.valueOf(stringObjectEntry.getValue())))
.toList();
log.warn("[CustomTags] [{}]", CommonUtils.toJson(tags));
return tags;
}
} catch (Exception e) {
if (PRINT_ERROR_COUNTER < 5) {
log.error("[Error while getting attributes map object]", e);
PRINT_ERROR_COUNTER++;
}
}
return List.of();
}
#Override
public Iterable<Tag> getLongRequestTags(HttpServletRequest request, Object handler) {
return null;
}
}
#Bean
public WebMvcTagsContributor webMvcTagsContributor() {
return new CustomWebMvcTagsContributor();
}
In order to test this, i've created a small spring boot app, added an endpoint to it. It works just fine.
The problem is when I add this code to the production app.
The metrics generates are the default ones and i can't figure out why.
What can I check to see why the tags are not added?
local test project
http_server_requests_seconds_count {exception="None", method="GET",id="123",outcome="Success",status="200",test="test",uri="/test/{id}/compute/{test}",)1.0
in prod - different (& bigger) app
http_server_requests_seconds_count {exception="None", method="GET",outcome="Success",status="200",uri="/api/{something}/test",)1.0
What i've tried and didn't work
Created a bean that implemented WebMvcTagsProvider - this one had an odd behaviour - it wasn't creating metrics for endpoints that had path variables in the path - though in my local test project it worked as expected
I added that log there in order to see what the extra tags are but doesn't seem to reach there as i don't see anything in the logs - i know, you might say that the current user id stops it, but it's not that.
In my Sling app I have data presenting documents, with pages, and content nodes. We mostly server those documents as HTML, but now I would like to have a servlet to serve these documents as PDF and PPT.
Basically, I thought about implementing the factory pattern : in my servlet, dependending on the extension of the request (pdf or ppt), I would get from a DocumentBuilderFactory, the proper DocumentBuilder implementation, either PdfDocumentBuilder or PptDocumentBuilder.
So first I had this:
public class PlanExportBuilderFactory {
public PlanExportBuilder getBuilder(String type) {
PlanExportBuilder builder = null;
switch (type) {
case "pdf":
builder = new PdfPlanExportBuilder();
break;
default:
logger.error("Unsupported plan export builder, type: " + type);
}
return builder;
}
}
In the servlet:
#Component(metatype = false)
#Service(Servlet.class)
#Properties({
#Property(name = "sling.servlet.resourceTypes", value = "myApp/document"),
#Property(name = "sling.servlet.extensions", value = { "ppt", "pdf" }),
#Property(name = "sling.servlet.methods", value = "GET")
})
public class PlanExportServlet extends SlingSafeMethodsServlet {
#Reference
PlanExportBuilderFactory builderFactory;
#Override
protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response) throws ServletException, IOException {
Resource resource = request.getResource();
PlanExportBuilder builder = builderFactory.getBuilder(request.getRequestPathInfo().getExtension());
}
}
But the problem is that in the builder I would like to reference other services to access Sling resources, and with this solution, they're not bound.
I looked at Services Factory with OSGi but from what I've understood, you use them to configure differently the same implementation of a service.
Then I found that you can get a specific implementation by naming it, or use a property and a filter.
So I've ended up with this:
public class PlanExportBuilderFactory {
#Reference(target = "(builderType=pdf)")
PlanExportBuilder pdfPlanExportBuilder;
public PlanExportBuilder getBuilder(String type) {
PlanExportBuilder builder = null;
switch (type) {
case "pdf":
return pdfPlanExportBuilder;
default:
logger.error("Unsupported plan export builder, type: " + type);
}
return builder;
}
}
The builder defining a "builderType" property :
// AbstractPlanExportBuilder implements PlanExportBuilder interface
#Component
#Service(value=PlanExportBuilder.class)
public class PdfPlanExportBuilder extends AbstractPlanExportBuilder {
#Property(name="builderType", value="pdf")
public PdfPlanExportBuilder() {
planDocument = new PdfPlanDocument();
}
}
I would like to know if it's a good way to retrieve my PDF builder implementation regarding OSGi good practices.
EDIT 1
From Peter's answer I've tried to add multiple references but with Felix it doesn't seem to work:
#Reference(name = "planExportBuilder", cardinality = ReferenceCardinality.MANDATORY_MULTIPLE, policy = ReferencePolicy.DYNAMIC)
private Map<String, PlanExportBuilder> builders = new ConcurrentHashMap<String, PlanExportBuilder>();
protected final void bindPlanExportBuilder(PlanExportBuilder b, Map<String, Object> props) {
final String type = PropertiesUtil.toString(props.get("type"), null);
if (type != null) {
this.builders.put((String) props.get("type"), b);
}
}
protected final void unbindPlanExportBuilder(final PlanExportBuilder b, Map<String, Object> props) {
final String type = PropertiesUtil.toString(props.get("type"), null);
if (type != null) {
this.builders.remove(type);
}
}
I get these errors :
#Reference(builders) : Missing method bind for reference planExportBuilder
#Reference(builders) : Something went wrong: false - true - MANDATORY_MULTIPLE
#Reference(builders) : Missing method unbind for reference planExportBuilder
The Felix documentation here http://felix.apache.org/documentation/subprojects/apache-felix-maven-scr-plugin/scr-annotations.html#reference says for the bind method:
The default value is the name created by appending the reference name to the string bind. The method must be declared public or protected and take single argument which is declared with the service interface type
So according to this, I understand it cannot work with Felix, as I'm trying to pass two arguments. However, I found an example here that seems to match what you've suggested but I cannot make it work: https://github.com/Adobe-Consulting-Services/acs-aem-samples/blob/master/bundle/src/main/java/com/adobe/acs/samples/services/impl/SampleMultiReferenceServiceImpl.java
EDIT 2
Just had to move the reference above the class to make it work:
#References({
#Reference(
name = "planExportBuilder",
referenceInterface = PlanExportBuilder.class,
policy = ReferencePolicy.DYNAMIC,
cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE)
})
public class PlanExportServlet extends SlingSafeMethodsServlet {
Factories are evil :-) Main reason is of course the yucky class loading hacks that are usually used but also because they tend to have global knowledge. In general, you want to be able to add a bundle with a new DocumentBuilder and then that type should become available.
A more OSGi oriented solution is therefore to use service properties. This could look like:
#Component( property=HTTP_WHITEBOARD_FILTER_REGEX+"=/as")
public class DocumentServlet {
final Map<String,DocBuilder> builders = new ConcurrentHashMap<>();
public void doGet( HttpServletRequest rq, HttpServletResponse rsp )
throws IOException, ServletException {
InputStream in = getInputStream( rq.getPathInfo() );
if ( in == null )
....
String type = toType( rq.getPathInfo(), rq.getParameter("type") );
DocBuilder docbuilder = builders.get( type );
if ( docbuilder == null)
....
docbuilder.convert( type, in, rsp.getOutputStream() );
}
#Reference( cardinality=MULTIPLE, policy=DYNAMIC )
void addDocBuilder( DocBuilder db, Map<String,Object> props ) {
docbuilders.put(props.get("type"), db );
}
void removeDocBuilder(Map<String,Object> props ) {
docbuilders.remove(props.get("type"));
}
}
A DocBuilder could look like:
#Component( property = "type=ppt-pdf" )
public class PowerPointToPdf implements DocBuilder {
...
}
One of the request that comes to my Zuul Filter is of URI /hello/World which i want to redirect to /myapp/test. This /myapp/test is a service that is registered in Eureka.
zuul:
routes:
xyz:
path: /hello/World
url: http://localhost:1234/myapp/test
stripPrefix: true
When i try the above configuration, the incoming URI is suffixed to the configured URL like http://localhost:1234/myapp/test/World . Few of the links which i came across seem to be stating that URL Rewrite feature is not yet available in Zuul.
Is there any other way this can be done at the Zuul Layer ?
Note: At this point of time, i cannot do this reverse proxying in the Webserver or any other layer since, my Zuul filter is the one that is receiving the request directly.
Using #Adelin solution, with little improvements
Use 'url' property as path to prepend for customizing the Url rewriting (I have disabled Eureka in my example) :
ribbon.eureka.enabled=false
zuul.routes.route1.path=/route1/**
zuul.routes.route1.serviceId=service1
zuul.routes.route1.url=/path/to/prepend
service1.ribbon.listOfServers=http://server1
Then implement the following filter :
/**
* Fixing missing URL rewriting when using ribbon
*/
#Component
public class CustomPathZuulFilter extends ZuulFilter {
#Autowired
private ZuulProperties zuulProperties;
#Override
public String filterType() {
return FilterConstants.PRE_TYPE;
}
#Override
public int filterOrder() {
return FilterConstants.PRE_DECORATION_FILTER_ORDER + 1;
}
#Override
public boolean shouldFilter() {
// override PreDecorationFilter only if executed previously successfully
return RequestContext.getCurrentContext().getFilterExecutionSummary().toString()
.contains("PreDecorationFilter[SUCCESS]");
}
#Override
public Object run() {
final RequestContext context = RequestContext.getCurrentContext();
if (context.get(FilterConstants.SERVICE_ID_KEY) == null || context.getRouteHost() != null) {
// not a Ribbon route
return null;
}
// get current ZuulRoute
final String proxy = (String) context.get(FilterConstants.PROXY_KEY);
final ZuulRoute zuulRoute = this.zuulProperties.getRoutes().get(proxy);
// patch URL by prefixing it with zuulRoute.url
final Object originalRequestPath = context.get(FilterConstants.REQUEST_URI_KEY);
final String modifiedRequestPath = zuulRoute.getUrl() + originalRequestPath;
context.put(FilterConstants.REQUEST_URI_KEY, modifiedRequestPath);
// patch serviceId because :
// - has been set to route.location in PreDecorationFilter
// - route.location has been set to zuulRoute.location in SimpleRouteLocator
// - zuulRoute.location return zuulRoute.url if set
context.set(FilterConstants.SERVICE_ID_KEY, zuulRoute.getServiceId());
return null;
}
}
Now calls to /route1 will be proxified to http://server1/path/to/prepend
This solution is also compatible with co-existing routes not using Ribbon.
Example of a co-existing route not using Ribbon :
zuul.routes.route2.path=/route2/**
zuul.routes.route2.url=http://server2/some/path
Calls to /route2 will be proxified to http://server2/some/path by SimpleHostRoutingFilter (if not disabled)
Here is a posted solution in the link by #Vikash
#Component
public class CustomPathZuulFilter extends ZuulFilter
{
#Override
public String filterType() {
return "pre";
}
#Override
public int filterOrder() {
return PreDecorationFilter.FILTER_ORDER + 1;
}
#Override
public boolean shouldFilter() {
return true;
}
#Override
public Object run() {
RequestContext context = RequestContext.getCurrentContext();
Object originalRequestPath = context.get(REQUEST_URI_KEY);
String modifiedRequestPath = "/api/microservicePath" + originalRequestPath;
context.put(REQUEST_URI_KEY, modifiedRequestPath);
return null;
}
}
Have you tried creating a preFilter or even a routeFilter ?
That way you can intercept the request, and change the routing.
See Zuul Filters
I want my response to include this:
"keyMaps":{
"href":"http://localhost/api/keyMaps{/keyMapId}",
"templated":true
}
That's easy enough to achieve:
add(new Link("http://localhost/api/keyMaps{/keyMapId}", "keyMaps"));
But, of course, I'd rather use the ControllerLinkBuilder, like this:
add(linkTo(methodOn(KeyMapController.class).getKeyMap("{keyMapId}")).withRel("keyMaps"));
The problem is that by the time the variable "{keyMapId}" reaches the UriTemplate constructor, it's been included in an encoded URL:
http://localhost/api/keyMaps/%7BkeyMapId%7D
So UriTemplate's constructor doesn't recognise it as containing a variable.
How can I persuade ControllerLinkBuilder that I want to use template variables?
It looks to me like the current state of Spring-HATEOAS doesn't allow this via the ControllerLinkBuilder (I'd very much like to be proven wrong), so I have implemented this myself using the following classes for templating query parameters:
public class TemplatedLinkBuilder {
private static final TemplatedLinkBuilderFactory FACTORY = new TemplatedLinkBuilderFactory();
public static final String ENCODED_LEFT_BRACE = "%7B";
public static final String ENCODED_RIGHT_BRACE = "%7D";
private UriComponentsBuilder uriComponentsBuilder;
TemplatedLinkBuilder(UriComponentsBuilder builder) {
uriComponentsBuilder = builder;
}
public static TemplatedLinkBuilder linkTo(Object invocationValue) {
return FACTORY.linkTo(invocationValue);
}
public static <T> T methodOn(Class<T> controller, Object... parameters) {
return DummyInvocationUtils.methodOn(controller, parameters);
}
public Link withRel(String rel) {
return new Link(replaceTemplateMarkers(uriComponentsBuilder.build().toString()), rel);
}
public Link withSelfRel() {
return withRel(Link.REL_SELF);
}
private String replaceTemplateMarkers(String encodedUri) {
return encodedUri.replaceAll(ENCODED_LEFT_BRACE, "{").replaceAll(ENCODED_RIGHT_BRACE, "}");
}
}
and
public class TemplatedLinkBuilderFactory {
private final ControllerLinkBuilderFactory controllerLinkBuilderFactory;
public TemplatedLinkBuilderFactory() {
this.controllerLinkBuilderFactory = new ControllerLinkBuilderFactory();
}
public TemplatedLinkBuilder linkTo(Object invocationValue) {
ControllerLinkBuilder controllerLinkBuilder = controllerLinkBuilderFactory.linkTo(invocationValue);
UriComponentsBuilder uriComponentsBuilder = controllerLinkBuilder.toUriComponentsBuilder();
Assert.isInstanceOf(DummyInvocationUtils.LastInvocationAware.class, invocationValue);
DummyInvocationUtils.LastInvocationAware invocations = (DummyInvocationUtils.LastInvocationAware) invocationValue;
DummyInvocationUtils.MethodInvocation invocation = invocations.getLastInvocation();
Object[] arguments = invocation.getArguments();
MethodParameters parameters = new MethodParameters(invocation.getMethod());
for (MethodParameter requestParameter : parameters.getParametersWith(RequestParam.class)) {
Object value = arguments[requestParameter.getParameterIndex()];
if (value == null) {
uriComponentsBuilder.queryParam(requestParameter.getParameterName(), "{" + requestParameter.getParameterName() + "}");
}
}
return new TemplatedLinkBuilder(uriComponentsBuilder);
}
}
Which embeds the normal ControllerLinkBuilder and then uses similar logic to parse for #RequestParam annotated parameters that are null and add these on to the query parameters. Also, our client resuses these templated URIs to perform further requests to the server. To achieve this and not need to worry about stripping out the unused templated params, I have to perform the reverse operation (swapping {params} with null), which I'm doing using a custom Spring RequestParamMethodArgumentResolver as follows
public class TemplatedRequestParamResolver extends RequestParamMethodArgumentResolver {
public TemplatedRequestParamResolver() {
super(false);
}
#Override
protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest webRequest) throws Exception {
Object value = super.resolveName(name, parameter, webRequest);
if (value instanceof Object[]) {
Object[] valueAsCollection = (Object[])value;
List<Object> resultList = new LinkedList<Object>();
for (Object collectionEntry : valueAsCollection) {
if (nullifyTemplatedValue(collectionEntry) != null) {
resultList.add(collectionEntry);
}
}
if (resultList.isEmpty()) {
value = null;
} else {
value = resultList.toArray();
}
} else{
value = nullifyTemplatedValue(value);
}
return value;
}
private Object nullifyTemplatedValue(Object value) {
if (value != null && value.toString().startsWith("{") && value.toString().endsWith("}")) {
value = null;
}
return value;
}
}
Also this needs to replace the existing RequestParamMethodArgumentResolver which I do with:
#Configuration
public class ConfigureTemplatedRequestParamResolver {
private #Autowired RequestMappingHandlerAdapter adapter;
#PostConstruct
public void replaceArgumentMethodHandlers() {
List<HandlerMethodArgumentResolver> argumentResolvers = new ArrayList<HandlerMethodArgumentResolver>(adapter.getArgumentResolvers());
for (int cursor = 0; cursor < argumentResolvers.size(); ++cursor) {
HandlerMethodArgumentResolver handlerMethodArgumentResolver = argumentResolvers.get(cursor);
if (handlerMethodArgumentResolver instanceof RequestParamMethodArgumentResolver) {
argumentResolvers.remove(cursor);
argumentResolvers.add(cursor, new TemplatedRequestParamResolver());
break;
}
}
adapter.setArgumentResolvers(argumentResolvers);
}
}
Unfortunately, although { and } are valid characters in a templated URI, they are not valid in a URI, which may be a problem for your client code depending on how strict it is. I'd much prefer a neater solution built into Spring-HATEOAS!
With latest versions of spring-hateoas you can do the following:
UriComponents uriComponents = UriComponentsBuilder.fromUri(linkBuilder.toUri()).build();
UriTemplate template = new UriTemplate(uriComponents.toUriString())
.with("keyMapId", TemplateVariable.SEGMENT);
will give you: http://localhost:8080/bla{/keyMapId}",
Starting with this commit:
https://github.com/spring-projects/spring-hateoas/commit/2daf8aabfb78b6767bf27ac3e473832c872302c7
You can now pass null where path variable is expected. It works for me, without workarounds.
resource.add(linkTo(methodOn(UsersController.class).someMethod(null)).withRel("someMethod"));
And the result:
"someMethod": {
"href": "http://localhost:8080/api/v1/users/{userId}",
"templated": true
},
Also check related issues: https://github.com/spring-projects/spring-hateoas/issues/545
We've run into the same problem. General workaround is we have our own LinkBuilder class with a bunch of static helpers. Templated ones look like this:
public static Link linkToSubcategoriesTemplated(String categoryId){
return new Link(
new UriTemplate(
linkTo(methodOn(CategoryController.class).subcategories(null, null, categoryId))
.toUriComponentsBuilder().build().toUriString(),
// register it as variable
getBaseTemplateVariables()
),
REL_SUBCATEGORIES
);
}
private static TemplateVariables getBaseTemplateVariables() {
return new TemplateVariables(
new TemplateVariable("page", TemplateVariable.VariableType.REQUEST_PARAM),
new TemplateVariable("sort", TemplateVariable.VariableType.REQUEST_PARAM),
new TemplateVariable("size", TemplateVariable.VariableType.REQUEST_PARAM)
);
}
This is for exposing the parameters of a controller response of a PagedResource.
then in the controllers we call this an append a withRel as needed.
According to this issue comment, this will be addressed in an upcoming release of spring-hateoas.
For now, there's a drop-in replacement for ControllerLinkBuilder available from de.escalon.hypermedia:spring-hateoas-ext in Maven Central.
I can now do this:
import static de.escalon.hypermedia.spring.AffordanceBuilder.*
...
add(linkTo(methodOn(KeyMapController.class).getKeyMap(null)).withRel("keyMaps"));
I pass in null as the parameter value to indicate I want to use a template variable. The name of the variable is automatically pulled from the controller.
I needed to include a link with template variables in the root of a spring data rest application, to get access via traverson to an oauth2 token. This is working fine, maybe useful:
#Component
class RepositoryLinksResourceProcessor implements ResourceProcessor<RepositoryLinksResource> {
#Override
RepositoryLinksResource process(RepositoryLinksResource resource) {
UriTemplate uriTemplate = new UriTemplate(
ControllerLinkBuilder.
linkTo(
TokenEndpoint,
TokenEndpoint.getDeclaredMethod("postAccessToken", java.security.Principal, Map )).
toUriComponentsBuilder().
build().
toString(),
new TemplateVariables([
new TemplateVariable("username", TemplateVariable.VariableType.REQUEST_PARAM),
new TemplateVariable("password", TemplateVariable.VariableType.REQUEST_PARAM),
new TemplateVariable("clientId", TemplateVariable.VariableType.REQUEST_PARAM),
new TemplateVariable("clientSecret", TemplateVariable.VariableType.REQUEST_PARAM)
])
)
resource.add(
new Link( uriTemplate,
"token"
)
)
return resource
}
}
Based on the previous comments I have implemented a generic helper method (against spring-hateoas-0.20.0) as a "temporary" workaround. The implementation does consider only RequestParameters and is far from being optimized or well tested. It might come handy to some other poor soul traveling down the same rabbit hole though:
public static Link getTemplatedLink(final Method m, final String rel) {
DefaultParameterNameDiscoverer disco = new DefaultParameterNameDiscoverer();
ControllerLinkBuilder builder = ControllerLinkBuilder.linkTo(m.getDeclaringClass(), m);
UriTemplate uriTemplate = new UriTemplate(UriComponentsBuilder.fromUri(builder.toUri()).build().toUriString());
Annotation[][] parameterAnnotations = m.getParameterAnnotations();
int param = 0;
for (Annotation[] parameterAnnotation : parameterAnnotations) {
for (Annotation annotation : parameterAnnotation) {
if (annotation.annotationType().equals(RequestParam.class)) {
RequestParam rpa = (RequestParam) annotation;
String parameterName = rpa.name();
if (StringUtils.isEmpty(parameterName)) parameterName = disco.getParameterNames(m)[param];
uriTemplate = uriTemplate.with(parameterName, TemplateVariable.VariableType.REQUEST_PARAM);
}
}
param++;
}
return new Link(uriTemplate, rel);
}
Suppose I have a Website that is used in normal mode (browser) and in some other mode, like a MobileView mode (inside a mobile app). For each Controller I create, there might be correspondent controller for MobileView, processing the same url.
The easiest solution is to create ifs in all the Controllers that have MobileView logic. Another solution would be to use a correspondent url for MobileView (similar to the normal url) and two separate Controllers (possible where one extends from another; or use some other way to recycle common code)
But, a more elegant solution would be to have some extra annotations, like #SupportsMobileView (to mark a controller, and tell the app that this will have a correspondent MobileView Controller) and #MobileViewController (to mark a second controller, and tell the app that this controller needs to run immediately after the initial controller marked with #SupportsMobileView). The link between a normal controller and a MobileView controller would be through the url they process (defined with #RequestMapping).
Is it possible to extend Spring MVC (A)? Where to inject new annotation scanners (B) and annotation handlers / component handlers (C)? How should the MobileView controller be executed (D) (right now I am thinking that it could be executed through AOP, where the new handler of my new controller type programatically creates a Join-Point on the corresponding normal controller)
Note that I did not mention how this MobileView mode is triggered and detected. Let's just say that there a Session boolean variable (flag) for that.
Critics on any points (A), (B), (C) or (D) are welcomed, as well as technical hints and alternative solution to any point or the whole solution.
HandlerInterceptor can be used to intercept the RequestMapping handling. This is a simple example how to configure and implement one.
You can check for your session variable and will have a bunch of methods that will allow you to do custom processing or just exchange the view from the normal controller handling with your mobile view.
Ok, warnings:
this is only a proof of concept of what I understood must be done so:
+#MobileViewEnable and #MobileView annotated (and related) methods need to stay in the same controller
+there's no check for the httpAction used
+the two methods must have the same signature
+mobileView annotation value and requestMapping annotation value must be equals and uniques
+the logic inside callYourLogic(..) defines which method is going to be called, at the moment there's a very simple logic that check if exist the parameter ("mobile") in the request, just to test
+this code is not intended to be used as is (at all)
+don't know if it works at all outside my pc (joke :D, ehm..)
SO:
Annotations:
#Retention(RetentionPolicy.RUNTIME)
public #interface MobileView {
String value() default "";
}
#Retention(RetentionPolicy.RUNTIME)
public #interface MobileViewEnable {
}
ExampleController:
#Controller
public class MainController extends BaseController {
private final static Logger logger = LoggerFactory.getLogger(MainController.class);
private final static String PROVA_ROUTE = "prova";
#MobileViewEnable
#RequestMapping(PROVA_ROUTE)
public String prova() {
logger.debug("inside prova!!!");
return "provaview";
}
#MobileView(PROVA_ROUTE)
public String prova2() {
logger.debug("inside prova2!!!");
return "prova2view";
}
}
Aspect definition:
<bean id="viewAspect" class="xxx.yyy.ViewAspect" />
<aop:config>
<aop:pointcut expression="#annotation(xxx.yyy.MobileViewEnable)" id="viewAspectPointcut" />
<aop:aspect ref="viewAspect" order="1">
<aop:around method="around" pointcut-ref="viewAspectPointcut" arg-names="viewAspectPointcut"/>
</aop:aspect>
</aop:config>
Aspect implementation:
public class ViewAspect implements BeforeAdvice, ApplicationContextAware {
private final static Logger logger = LoggerFactory.getLogger(ViewAspect.class);
private ApplicationContext applicationContext;
public Object around(ProceedingJoinPoint joinPoint) {
Method mobileViewAnnotatedMethod = null;
HttpServletRequest request = getCurrentHttpRequest();
String controllerName = getSimpleClassNameWithFirstLetterLowercase(joinPoint);
Object[] interceptedMethodArgs = getInterceptedMethodArgs(joinPoint);
String methodName = getCurrentMethodName(joinPoint);
Method[] methods = getAllControllerMethods(joinPoint);
Method interceptedMethod = getInterceptedMethod(methods, methodName);
String interceptedMethodRoute = getRouteFromInterceptedMethod(interceptedMethod);
if (callYourLogic(request)) {
mobileViewAnnotatedMethod = getMobileViewAnnotatedMethodWithRouteName(methods, interceptedMethodRoute);
if (mobileViewAnnotatedMethod != null)
return invokeMethod(mobileViewAnnotatedMethod, interceptedMethodArgs, controllerName);
}
return continueInterceptedMethodExecution(joinPoint, interceptedMethodArgs);
}
private Object continueInterceptedMethodExecution(ProceedingJoinPoint joinPoint, Object[] interceptedMethodArgs) {
try {
return joinPoint.proceed(interceptedMethodArgs);
} catch (Throwable e) {
logger.error("unable to proceed with intercepted method call: " + e);
}
return null;
}
private Object[] getInterceptedMethodArgs(JoinPoint joinPoint) {
return joinPoint.getArgs();
}
private boolean callYourLogic(HttpServletRequest request) {
// INSERT HERE YOUR CUSTOM LOGIC (e.g.: is the server accessed from a mobile device?)
// THIS IS A STUPID LOGIC USED ONLY FOR EXAMPLE
return request.getParameter("mobile")!= null;
}
private HttpServletRequest getCurrentHttpRequest() {
return ((ServletRequestAttributes) RequestContextHolder.currentRequestAttributes()).getRequest();
}
private String invokeMethod(Method method, Object[] methodArgs, String className) {
if (method != null) {
try {
Object classInstance = getInstanceOfClass(method, className);
return (String) method.invoke(classInstance, methodArgs);
} catch (Exception e) {
logger.error("unable to invoke method" + method + " - " + e);
}
}
return null;
}
private Object getInstanceOfClass(Method method, String className) {
return applicationContext.getBean(className);
}
private Method getMobileViewAnnotatedMethodWithRouteName(Method[] methods, String routeName) {
for (Method m : methods) {
MobileView mobileViewAnnotation = m.getAnnotation(MobileView.class);
if (mobileViewAnnotation != null && mobileViewAnnotation.value().equals(routeName))
return m;
}
return null;
}
private String getRouteFromInterceptedMethod(Method method) {
RequestMapping requestMappingAnnotation = method.getAnnotation(RequestMapping.class);
if (requestMappingAnnotation != null)
return requestMappingAnnotation.value()[0];
return null;
}
private String getCurrentMethodName(JoinPoint joinPoint) {
return joinPoint.getSignature().getName();
}
private Method[] getAllControllerMethods(JoinPoint joinPoint) {
return joinPoint.getThis().getClass().getSuperclass().getMethods();
}
private String getSimpleClassNameWithFirstLetterLowercase(JoinPoint joinPoint) {
String simpleClassName = joinPoint.getThis().getClass().getSuperclass().getSimpleName();
return setFirstLetterLowercase(simpleClassName);
}
private String setFirstLetterLowercase(String simpleClassName) {
String firstLetterOfTheString = simpleClassName.substring(0, 1).toLowerCase();
String restOfTheString = simpleClassName.substring(1);
return firstLetterOfTheString + restOfTheString;
}
private Method getInterceptedMethod(Method[] methods, String lookingForMethodName) {
for (Method m : methods)
if (m.getName().equals(lookingForMethodName))
return m;
return null;
}
#Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}