In this guide, we will learn Jersey(JAX-RS) Resources and Sub Resources concepts as well as mapping of API HTTP URI using @Path annotation. Specifically, we will go through the following concepts and examples:
- Root Resources (Resources)
- Sub Resources
- HTTP URL mapping to Resources and Sub Resources using @Path annotation
- Deep dive @Path annotation
- Understand @PathParam annotation
We had tested or used the following tools and technologies in this project:
- Jersey (v 2.21)
- Gradle Build System (v 2.9)
- Spring Boot (v 1.3)
- Java (v 1.8)
- Eclipse IDE
This is a part of Jersey (JAX-RS) Restful Web Services Development Guides series. Please read Jersey + Spring Boot getting started guide._
Understand Resources & Sub Resources
In the real world we will be developing an API for either Resources or Non-Resources items. Usually, a standard API URL looks like the below for Resources:
Get a list of all humans – https://localhost:8080/humans
Get a specific human – https://localhost:8080/humans**/40200/**
Get a list of all addresses of a specific human – https://localhost:8080/humans**/40200/addresses/**
Get a specific address of a specific human – https://localhost:8080/humans**/40200/addresses/2/**
Note: Other than the bold part everything is base URI.
In the above examples, We are talking about Human Resources. Human Resources has relation with Address Resources. Or We may say Address Resources is Sub Resources of Human Resources. We may represent Address Resources as independent Resources as well as Sub Resources. When we design API for representing relationship data we opt for Sub Resources.
Tip: Resources like the Humans in the above example can also be called Root Resources.
Let’s understand, how we can map Resources and Sub Resources to URI
Examples Resource & Sub Resource URI mapping using @Path
Resource class level URI mapping using @Path
Mapping /Humans
File: HumansResource.java
package in.geekmj.jersey.resource;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
@Path("Humans")
public class HumansResource {
/**
*
* @return Response
*/
@GET
@Produces("text/plain")
public Response getHumans() {
return Response.accepted("Test /Human api called successfully.").build();
}
}
Access URL https://localhost:8080/Humans
Test /human API called successfully.
Like @GET we can also use @POST, @PUT, and @DELETE.
Read URI Path Parameter using @PathParam
Mapping /humans/40200 or /humans/123445 or /humans/ and extracting humanId from path and using it in the method with the help of @PathParam annotation.
File: HumansResource.java
package in.geekmj.jersey.resource;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
@Path("humans")
public class HumansResource {
@GET
@Path("{humanId}")
@Produces("text/plain")
public Response getHuman(@PathParam("humanId") int humanId) {
return Response.accepted("Test /human/" + humanId + " api called successfully.").build();
}
}
Access URL https://localhost:8080/humans/40200
Test /human/40200 API called successfully.
Sub Resources URI Mapping using @Path at method level
Mapping /humans/123442/addresses
File: HumansResource.java
package in.geekmj.jersey.resource;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
@Path("humans")
public class HumansResource {
@GET
@Path("{humanId}/addresses")
@Produces("text/plain")
public Response getAddresses(@PathParam("humanId") int humanId) {
return Response.accepted("Test /human/" + humanId + "/addresses api called successfully.").build();
}
}
Access URL https://localhost:8080/humans/40200/addresses
Test /humans/40200/addresses API called successfully.
Read Sub Resource URI Path Parameter using @PathParam
Mapping /humans/123442/addresses/2
File: HumansResource.java
package in.geekmj.jersey.resource;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
@Path("humans")
public class HumansResource {
@GET
@Path("{humanId}/addresses/{addressId}")
@Produces("text/plain")
public Response getAddress(@PathParam("humanId") int humanId, @PathParam("addressId") int addressId) {
return Response.accepted(
"Test /human/" + humanId + "/addresses/addresses/" + addressId + " api called successfully.")
.build();
}
}
Access URL https://localhost:8080/humans/40200/addresses/2
Test /humans/40200/addresses/2 API called successfully.
Validate path parameter with Regular Expression in @Path
If we wanted to confirm the path parameter(s) value we may express the expected values using regular expression in @Path.
For e.g. if we wanted to only accept numbers for human id then we express that like @Path(“humans/{humanId: [0-9]*}”)
File: HumansResource.java
package in.geekmj.jersey.resource;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
@Path("humans")
public class HumansResource {
@GET
@Path("{humanId: [0-9]*}")
@Produces("text/plain")
public Response getHuman(@PathParam("humanId") int humanId) {
return Response.accepted("Test /human/" + humanId + " api called successfully.").build();
}
}
Access URL https://localhost:8080/humans/40200
Test /human/40200 API called successfully.
If we access the URL https://localhost:8080/humans/40200abc ; It will give you an HTTP 404 error.
Tip: Default Regular Expression is {pathParam: [^/]+}. You can use any regular expression to confirm the Path Parameter values.
Another Tip: We are free to use or not use beginning / (forward slash) in URI. They don’t make any difference.
Infographics to remember what we talked about in this guide (Read Employee as Human):
