{"id":51559,"date":"2016-02-01T22:00:49","date_gmt":"2016-02-01T20:00:49","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/?p=51559"},"modified":"2016-02-01T19:43:28","modified_gmt":"2016-02-01T17:43:28","slug":"java-ee-8-mvc-working-path-parameters","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2016\/02\/java-ee-8-mvc-working-path-parameters.html","title":{"rendered":"Java EE 8 MVC: Working with Path Parameters"},"content":{"rendered":"

In the previous post we saw how to work with query parameters in Java EE MVC<\/a>. This post continues with a very similar topic: path parameters.<\/p>\n

Path parameters are a dynamic part of the request path and can be specified with the @Path annotation.<\/p>\n

For example:<\/p>\n

@Controller\r\n@Path(\"path-params\")\r\npublic class PathParamsController {\r\n\r\n  @GET\r\n  @Path(\"\/date\/{year}\/{month}\")\r\n  public String pathParamDate(@PathParam(\"year\") int year, @PathParam(\"month\") int month) {\r\n    ...\r\n  }\r\n}<\/pre>\n
Paths parameter are surrounded with curly brackets inside the @Path annotation. In this example two path parameters are defined: year and month.<\/p>\n
With @PathParam path parameters can be mapped to method parameters.<\/p>\n
We can call this method by sending a request to<\/p>\n
\/path-params\/date\/2016\/01<\/pre>\n
In this case 2016 and 1 will be passed as year and month arguments.<\/p>\n
Type conversion<\/h2>\n
Path parameters use the same type conversion rules as query parameters (explained in the previous blog post<\/a>).<\/p>\n
For example, we can convert a path parameter to an enum value like this:
 
<\/div> <\/div><\/p>\n
public enum Role {\r\n  admin, reporter, accountant\r\n}<\/pre>\n
@Controller\r\n@Path(\"path-params\")\r\npublic class PathParamsController {\r\n\r\n  @GET\r\n  @Path(\"\/roles\/{role}\")\r\n  public String pathParamUsers(@PathParam(\"role\") Role role) {\r\n    ...\r\n  }\r\n}<\/pre>\n
If we now send a request to<\/p>\n
\/path-params\/roles\/admin<\/pre>\n
the string admin gets converted to the corresponding enum constant.<\/p>\n
Using @PathParam on fields and methods<\/h2>\n
Like @QueryParam the usage of @PathParam is not limited to method parameters. It is also possible to annotate fields or setters with @PathParam.<\/p>\n
For example:<\/p>\n
@Controller\r\n@Path(\"path-params\")\r\npublic class PathParamsController {\r\n\r\n  @PathParam(\"category\")\r\n  private String category;\r\n\r\n  @GET\r\n  @Path(\"\/categories\/{category}\")\r\n  public String findByCategory() {\r\n    \/\/ work with category\r\n  }\r\n}<\/pre>\n
Using Path Parameters with Patterns<\/h2>\n
It is possible to define a more specific pattern for a path variable. Therefore, a regular expression can be added after the name of the path variable.<\/p>\n
For example:<\/p>\n
@Controller\r\n@Path(\"path-params\")\r\npublic class PathParamsController {\r\n\r\n  @GET\r\n  @Path(\"\/users\/{id : \\\\d+}\")\r\n  public String findUserById(@PathParam(\"id\") long id) {\r\n    ...\r\n  }\r\n\r\n  @GET\r\n  @Path(\"\/users\/{name : [a-zA-Z]+}\")\r\n  public String findUserByName(@PathParam(\"name\") String name) {\r\n    ...\r\n  }  \r\n}<\/pre>\n
Here we define two controller methods that listen on \/users\/{variable}:<\/p>\n