I am trying to make an API with Jetty Server, and I have this simple GET request:
#GET
public String helloWorld(){
return "Hello world";
}
In order to make a POST request, I assume that one must save the input to the Jetty server. I have tried to research for quite a while, but found nothing.
I imagine something like this:
#POST
public void Save(String stringToSave) {
// Save to DB?
}
You could likely google this but let me give you a quick overview. A Servlet is a chunk of code that is normally run during an HTTP action - GET, POST, etc. It is the original technology of the JavaEE world, having been released in the late 1990's.
A simple Java servlet, using modern annotations, would look something like:
#WebServlet(name = "SampleServlet", urlPatterns = "/sampleServlet")
public class SampleServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// called when an HTTP POST is sent
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// called when an HTTP GET is sent
}
}
The important parts to note are that the class extends HttpServlet and that you have to write code to pull data out of the request and push it into the response. This isn't bad to do but it does have to be done.
JAX-RS is a newer standard, aimed simplifying the creation of REST services. It too is a chunk of code that runs during an HTTP interaction.
A simple example of this would be:
#Path("/sampleService")
public class SampleService{
#Consumes({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
#Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
#POST
#Path("/v1/hello")
public Response sayHello( SomeObject someobject ) {
The code here is both simpler and a bit more complex. The use of annotations helps determine the path that the service exists on a URL (in this case /sampleService/v1/hello), the HTTP method, and the Content-Type for both the request and response. Additionally, if the SomeObject object is defined correctly, the JAX-RS framework will automatically deserialize the incoming JSON or XML payload into an object for you.
The Response object contains the HTTP response code (perhaps a teapot) and a response body. In this example, the body will be automatically serialized back to the requestor in a way that matches the Accept header of the HTTP request (i.e., JSON for an application/json Accept header and XML for application/xml).
Note that while not directly related the JAX-RS framework takes advantage of the Servlet framework. Indeed in JAX-RS you can access the HttpServletRequest and HttpServletResponse object in your methods.
Which way is "better"? In general I would recommend using JAX-RS where possible as it is the newer standard and is a bit easier to implement. However, if you do any work in the JavaEE world you're very likely to run into Servlet code so it's important to understand it too.
Note that both Servlets and JAX-RS require an application server of some sort. Jetty is one of those. Another very common one is Tomcat. The application server sets up the environment for your code and listens for incoming HTTP messages. When it gets one it looks to see if it knows how to handle the URL and routes to the appropriate place. In the servlet world the server routes solely on the URL. In the JAX-RS world the server routes on the URL and, if specified by the #Consumes annotation, the HTTP Content-Type header too.
There is much more but let's start there and see if it answers what you're after.
Related
I have a couple of sipring boot restfull APIs, that I want to communicate with, from a GWT based front-end. I've looked a bit on the Internet and found the RestyGWT framework, but as far as I've seen, all the documentation available is for using the embeded GWT server as a restfull API.
Can anyone please direct me to a usefull tutorial that I can follow.
Thanks to all.
I actually found a way to GET data through JsonPRequestBuilder, the problem now resides in POSTing data in json format.
final RequestBuilder reqBuilder = new RequestBuilder(httpMethod, url);
final Request request = reqBuilder.sendRequest(requestData, new RequestCallback()
{
#Override
public void onResponseReceived(Request request, Response response)
{
GWT.log(response.getText());
}
#Override
public void onError(Request request, Throwable exception)
{
}
}
httpMethod is something from com.google.gwt.http.client.Method like Method.GET
request is a String in which you pass the json.
response.getText will display the json.
To convert from object to json I would suggest to look at https://github.com/nmorel/gwt-jackson or https://github.com/vegegoku/gwt-jackson-apt (first one is older and has more features, second one is newer and better suited for future (GWT 3.0) but maybe has some features missing).
I'm new to Java server-side programming, my question is basically to get to a starting point using Servlets (low level without using spring mvc etc.) and then build my way up from there, coming from node.js background where a route definition would start with a function (app.get(request, response) {}, app.post(request, response) {} etc.), and the function would receive request and response in parameters for one of http methods (GET, POST, PUT, DELETE).
If someone can please help on the starting point of how do I define methods against a route (let's say /users) inside a servlet class that'd map to http methods while providing request and response in it's parameters.
My attempt
public class FirstServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException , IOException {
}
I believe what you want are Servlet mappings. You can also find a bit more info here
But basically this is the way you tell the webserver (e.g. Tomcat) what servlet to use to answer requests sent to a given url pattern. Thus you map the pattern with the servlet you want to use to serve it.
You can also find more info on the inner workings here.
Edit: If you want to handle all verbs you can use a service. From the first link:
You may have seen other servlet examples implement the doPost() and/or doGet() methods. These methods reply only to POST or GET requests; if you want to handle all request types from a single method, your servlet can simply implement the service() method. (However, if you choose to implement the service() method, you cannot implement the doPost() or doGet() methods, unless you call super.service() at the beginning of the service() method.) The HTTP servlet specification describes other methods used to handle other request types, but all of these methods are collectively referred to as service methods.
All the service methods take the same parameter arguments. An
HttpServletRequest provides information about the request, and your
servlet uses an HttpServletResponse to reply to the HTTP client. The
service method looks like the following:
public void service(HttpServletRequest req,
HttpServletResponse res) throws IOException { ... }
I'm trying to build an api with Google Cloud Endpoints.
As Cloud Endpoints does not provide authentication beside Googles own OAuth I try to build my own. Therefore I want to access the parameters provided for the API (for example #Named("token") token) inside a servlet filter.
Unfortunately I cannot find any of the provided information inside the httpRequest. Is that normal? Is there a possibility to access the parameters?
I would appreciate if someone could help me!
UPDATE:
With the infos from jirungaray I tried to build an authentication using headers but ran into the same problem. Used a REST-Client to send some headers as I could not figure out how to do this with the API Explorer. Inside my filter I try to access the token from the headers:
#Override
public void doFilter(
ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
HttpServletRequest httpRequest = (HttpServletRequest) request;
String authToken = httpRequest.getHeader(Constants.AUTH_TOKEN);
...
chain.doFilter(request, response);
}
The reason why I try to do something like this, is that I'm using Guice for Dependency Injection and want my token to be injected inside another object.
With Guice I have the following Provider using the token to inject a FacebookClient (using the token) per request.
#Provides
public FacebookClient getFacebookClientProvider(#Named("fbToken") Provider<String> fbToken) {
return new DefaultFacebookClient(fbToken.get(), Version.VERSION_2_2);
}
As described in the Guice wiki (SevletModule) this uses a sevlet filter to get the information from the request.
Is there any solution to achieve this kind of DI with Cloud Endpoints?
Philip,
Yes, it does makes sense you are getting an empty request. Your endpoint calls are first handled by Google (they receive the API calls) and then those are processed and sent to a handler in your app. As this is all done in the background it's very easy to miss that your endpoints aren't actually getting the same request you sent, they get a completely different request sent from Google's infrastructure.
Even though your approach should work including tokens info in url makes them easier to sniff, even if you use SSL or encrypt your params the token is there in plain sight.
For what you are trying to achieve I recommend you include the token as a header in your request and retrieve that header by accessing the HTTPRequest directly on the endpoint, this is injected automatically if you include an HTTPServletRequest param in you endpoint method.
eg.
public APIResponse doSomething(SomeComplexRquestModel request,
HttpServletRequest rawRequest) {
}
If you still feel you should go with your original approach just comment and I'll help you debug the issue.
I'm working on a legacy code (Spring 2.5.x, Java 1.5), where controller passes Http Servlet Request to view like this:
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
Map attributes = new HashMap();
attributes.put("httpRequest", request);
return new ModelAndView("/path/to/page.jsp", attributes);
}
However what happens is that httpRequest attribute does indeed exist in the JSP Page context, but it contains current request (JSP page) and not the original (controller). The passed request is being used to extract some information from the URL. It appears that I can get around that problem by using a bunch of "javax.servlet.forward.*" attributes. This however puzzles me as it is pretty simple thing and I'd be happy to get it to work anyways or at least know exactly why it doesn't work now. Anybody has any ideas?
To begin with, it is a bad idea to store the request as attribute of request. If you need specific data for the current request, you can retrieve it directly using ${requestContext}, if you need to access to the URL, use ${requestContext.requestURL}. If you need to access to parts of this URL to display it in client side, it would be better to parse the url in server side (controller) by first obtaining it using StringBuffer url = request.getRequestURL(); and then setting the required data as attributes.
I have two Java web applications that have a single servlet that gets mapped to a specific URL:
red.war/
WEB-INF/classes
com.me.myorg.red.RedServlet (maps to http://red.example.com/doStuff)
blue.war/
WEB-INF/classes
com.me.myorg.blue.BlueServlet (maps to http://blue.example.com/doStuff)
I want to put these application (I'm calling them my "backend apps") behind a "proxy app" (servlet) that will decide which of these two apps will ultimately service a client-side request.
This proxy web app would take an incoming HTTP request, and determines which of the 2 "backend apps" (red or blue) to forward the request onto. The request would then be forwarded on to either http://red.example.com/doStuff (and then processed by RedServlet#doGet(...)) or http://blue.example.com/doStuff (and then processed by BlueServlet#doGet(...)). The returned response from the backend app (again, either RedServlet#doGet(...) or BlueServlet#doGet(...)) would then be returned to the proxy servlet, and ultimately returned to the client.
In other words, in pseudo-code:
public class ProxyServlet extends HttpServlet {
#Override
public doGet(HttpServletRequest request, HttpServletResponse response) {
String forwardingAddress;
if(shouldBeRed(request))
forwardingAddress = "http://red.example.com/doStuff";
else
forwardingAddress = "http://blue.example.com/doStuff";
PrintWriter writer = response.getWriter();
writer.write(getResponseFromBackend(forwardingAddress, request));
}
private String getResponseFromBackend(String addr, HttpServletRequest req) {
// Somehow forward req to addr and get HTML response...
}
}
Is this possible? If so, how and what code would I need to write to make it work?
You could use a RequestDispatcher to forward your request in the following way:
RequestDispatcher dispatcher = httpRequest.getRequestDispatcher(forwardingAddress);
// here you have the choice whether to use include(..) or forward(..) see below
if(useInclude)
dispatcher.include(httpRequest, httpResponse);
else
dispatcher.forward(httpRequest, httpResponse);
... where useInlcude is set to your choice with the following options:
includeThis is probably what you want to do: Load the content from the forwardingAdress into your response.
This means you could even include multiple targets into a single response.
The client will not even realize this procedure nor does he need to be able to see the target document.
forwardSend a forward to the forwardingAddress. This will tell the client to submit a new request to the specified URL.
If you do it in a browser with developer tools, you will see a second request.
The client must be able to see and load the target URL.
You can only forward to a single target.
See, the following links, too:
RequestDispatcher javadoc, especially for the notes:
forward should be called before the response has been committed to the client (before response body output has been flushed). If the response already has been committed, this method throws an IllegalStateException. Uncommitted output in the response buffer is automatically cleared before the forward.
include: The request and response parameters must be either the same objects as were passed to the calling servlet's service method or be subclasses of the ServletRequestWrapper or ServletResponseWrapper classes that wrap them.
URLRewriteFilter examplealthough this example is implemented using a Filter instead of a Servlet the behavior is the same (Note: this example is part of a framework of mine and hence contains some overhead in the parent classes. Just have a look at the relevant section...)
Since there is not yet an approved answer I try to write how I see the solution to this request use apache-http-commons library. In addition I suggest to add a flush on writer.
public class ProxyServlet extends HttpServlet {
#Override
public doGet(HttpServletRequest request, HttpServletResponse response) {
String forwardingAddress;
if(shouldBeRed(request))
forwardingAddress = "http://red.example.com/doStuff";
else
forwardingAddress = "http://blue.example.com/doStuff";
PrintWriter writer = response.getWriter();
writer.write(getResponseFromBackend(forwardingAddress, request));
**writer.flush();**
}
private String getResponseFromBackend(String addr, HttpServletRequest req) {
HttpClient client = new HttpClient();
HttpMethod method = new GetMethod(url);
client.executeMethod(method);
String body=method.getResponseBodyAsString();
return body;
}
}