Thursday, November 21, 2013

RESTEasy tutorial part two: web parameters

 
webservicesIn the first RESTEasy tutorial we have learnt the basics about REST Web services and we have tested a simple RESTful Web service. In this tutorial we will show how to inject web application elements (form parameters, query parameters and more) into a RESTful Web service.


You can use the following annotations to bind HTTP requests to a RESTful web service:

@FormParam
@PathParam
@QueryParam
@HeaderParam
@CookieParam
@MatrixParam


Let's explore all the possible interactions.

@FormParam


The annotation @FormParam can be used to inject the parameters of a Web form into a RESTful Web service.
Here's an example:
resteasy tutorial
Here we are submitting a POST request containing two parameters email and password which are translated into the parameters "e" and "p" of the login method.
Here's the full example:
1.<form method="POST" action="login">
2. 
3.Email Address: <input type="text" name="email">
4.<br>
5.Password: <input type="text" name="password">
6.<input type="submit">
7. 
8.</form>
01.@Path("/")
02.public class LoginService
03.{
04. 
05. 
06.@Path("login")
07.@POST
08.public String login(@FormParam("email") String e, @FormParam("password") String p) {  
09.return "Logged with " + e + " " + p;
10.}
11.}
As an alternative, you can bind the parameters email and password at class level, which can be useful if you need to re-use the same parameters across different methods of the service.
1.public class User {
2. 
3.@FormParam("email")
4.private String email;
5.@FormParam("password")
6.private String password;
7. 
8.}
You would need to modify the REST method accordingly:
1.@POST
2.@Path("login")
3.public String login(@Form User form) {
4.return "Logged with " + form.email + " " + form.password;
5.}

@PathParam

The @PathParam annotation binds the value of a path segment to a resource method parameter. For example, the following method would intercept an HTTP GET like http://server:port/login/12345 and convert the PathParam "12345" into the String "id"
01.@Path("/")
02.public class LoginService
03.{
04. 
05.@GET
06.@Path("login/{zip}")
07.public String login(@PathParam("zip") String id) {
08.return "Id is " +id;
09.}
10.}
As for @FormParam, you can embed the @PathParam declaration at class level, if you prefer.

@QueryParam


The @QueryParam annotation binds the value of a path segment to a resource method parameter. For example, the following method would intercept an HTTP GET like http://server:port/login?zip=12345 and inject the query parameter "zip" into the method parameter "zip"
01.@Path("/")
02.public class LoginService
03.{
04. 
05.@GET
06.@Path("login/{zip}")
07.public String login(@QueryParam("zip") String zip) {
08.return "Id is " +id;
09.}
10. 
11.}
QueryParam can be convenientely used with the DefaultValue annotation so that you can avoid a null pointer exception if no query parameter is passed.
1.@GET
2.@Path("login/{zip}")
3.public String login(@DefaultValue("11111"@QueryParam("zip") String zip) {
4.return "Id is " +id;
5.}
As for @FormParam, you can embed the @PathParam declaration at class level, if you prefer.

@HeaderParam


The @HeaderParam annotation extracts information from the HTTP header and binds it to a method parameter. Example:
1.@GET
2.public String callService(@HeaderParam("User-Agent") String whichBrowser) {
3....
4.}

@CookieParam

The @CookieParam annotation reads an information stored as a cookie and binds it to a method parameter. Example:
1.@GET
2.public String callService(@CookieParam("sessionid") String sessionid) {
3....
4.}

@MatrixParam

The @MatrixParam annotation can be used to bind an expression containing several property=value to a method parameter. For example, supposing you were to invoke an URL like http://server:port/login;name=francesco;surname=marchioni
1.@GET
2.public String callService(@MatrixParam("name") String name,
3.@MatrixParam("surname") String surname) {
4....
5.}
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