Bad Request Error (400) or Not Found Error (404) during extracting request parameters in jax-rs - jax-rs

Question

In docs.oracle ( https://docs.oracle.com/javaee/7/tutorial/jaxrs002.htm ) about Extracting Request Parameters we have:
If the URI path template variable cannot be cast to the specified type, the JAX-RS runtime returns an HTTP 400 (“Bad Request”) error to the client.
If the #PathParam annotation cannot be cast to the specified type, the JAX-RS runtime returns an HTTP 404 (“Not Found”) error to the client.
Could someone explain the difference, maybe give an example?

Answer 1

I don't know why, but if you define method with path param and it fails on cast string to custom type, jax-rs (in my case jersey servlet) returns 404 error, and it's very strange and unexpected.
package com.example.jaxrs.api;
...
#GET
#Path("/{id}/info")
public Response info(#PathParam UUID id) { ... }
curl -X GET http://127.0.0.1:8080/api/123/info --> HTTP ERROR 404 Not Found
This behavior can be changed. Just create simple ExceptionMapper, catch the ParamException, and return correct "400 Bad Request" response.
package com.example.jaxrs.errors;
#Provider
public class PathParamExceptionMapper implements ExceptionMapper<ParamException> {
#Override
public Response toResponse(ParamException exception) {
return Response.status(Response.Status.BAD_REQUEST).build();
}
}
Do not forgot annotation #Provider and add the package with error handler to servlet init param.
<servlet>
<servlet-name>jersey-serlvet</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>com.example.jaxrs.api;com.example.jaxrs.errors</param-value>
</init-param>
</servlet>