{"id":51071,"date":"2016-01-18T10:00:46","date_gmt":"2016-01-18T08:00:46","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/?p=51071"},"modified":"2016-01-17T21:22:46","modified_gmt":"2016-01-17T19:22:46","slug":"java-ee-8-mvc-working-query-parameters","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2016\/01\/java-ee-8-mvc-working-query-parameters.html","title":{"rendered":"Java EE 8 MVC: Working with query parameters"},"content":{"rendered":"

In the previous post about the new Java EE MVC Framework we had a detailed look on Controllers<\/a>. In this and the following posts we will see how to access various types of request data in MVC Controllers.<\/p>\n

Java EE MVC makes heavy use of JAX-RS and most of the things we will see in this and the next posts are JAX-RS features. So, if you are familiar with JAX-RS you probably will not learn much new in this post.<\/p>\n

Query parameters<\/h2>\n

This post focuses on query parameters. If you read my Java EE MVC Getting started<\/a> post you might already know the @QueryParam<\/code> annotation. The most common use case of\u00a0 @QueryParam<\/code> is to map a query parameter to a controller method parameter.<\/p>\n

For example:<\/p>\n

@Controller\r\n@Path(\"query-params\")\r\npublic class QueryParamsController {\r\n\r\n  @GET\r\n  public String queryParams(@QueryParam(\"name\") String name) {\r\n    ...\r\n  }\r\n}<\/pre>\n
If we now send a HTTP GET request to:<\/p>\n
\/query-params?name=john<\/pre>\n
the string “john<\/code>” will be passed as name<\/code> parameter to the method queryParams()<\/code>.<\/p>\n
Type conversion<\/h2>\n
With @QueryParam<\/code> query parameters can automatically be converted to various types.<\/p>\n
For example:<\/p>\n
public enum Role {\r\n  admin, reporter, accountant\r\n}<\/pre>\n
@Controller\r\n@Path(\"query-params\")\r\npublic class QueryParamsController {\r\n\r\n  @GET\r\n  public String queryParams(\r\n      @QueryParam(\"id\") long id,\r\n      @QueryParam(\"name\") String name,\r\n      @QueryParam(\"role\") Role role) {\r\n\r\n    ...\r\n  }\r\n}<\/pre>\n
We can now send a request like this:
 
<\/div> <\/div><\/p>\n
\/query-params?id=42&name=john&role=admin<\/pre>\n
A query parameter can automatically converted to a type, if the target type matches one of the following rules:<\/p>\n