LibraryLink ToToggle FramesPrintFeedback

Injecting data from HTML forms

HTML forms are an easy means of getting information from a user and they are also easy to create. Form data can be used for HTTP GET requests and HTTP POST requests:

GET

When form data is sent as part of an HTTP GET request the data is appended to the URI as a set of query parameters. Injecting data from query parameters is discussed in Using query parameters.

POST

When form data is sent as part of an HTTP POST request the data is placed in the HTTP message body. The form data can be handled using a regular entity parameter that supports the form data. It can also be handled by using the @FormParam annotation to extract the data and inject the pieces into resource method parameters.

The javax.ws.rs.FormParam annotation extracts field values from form data and injects the value into resource method parameters. The annotation takes a single parameter that specifies the key of the field from which it extracts the values. The associated parameter must conform to the data types described in Supported data types.

[Important]Important

The JAX-RS API Javadoc states that the @FormParam annotation can be placed on fields, methods, and parameters. However, the @FormParam annotation is only meaningful when placed on resource method parameters.

Example 3.8 shows a resource method that injects form data into its parameters. The method assumes that the client's form includes three fields—title, tags, and body—that contain string data.