Low Level Streaming with JAX-RS StreamingOutput

When working with large data or files, it is recommended to stream the output rather than loading the entire response into memory. This helps protect the servers resources and avoids getting out of memory exceptions. The JAX-RS StreamingOutput class is a simple callback that can be implemented to send the entity in the response when the application wants to stream the output.

JAX-RS StreamingOutput Example

We create a new StreamingOutput using an anonymous inner class and override the write() method. Using this method we can write directly to the OutputStream. This example streams all numbers from 1 to 9999999. When this service is called, it’ll stream the response when the output stream is available.

package com.memorynotfound.rs;

import javax.ws.rs.*;
import javax.ws.rs.core.*;
import java.io.*;

@Path("/numbers")
public class NumbersResource {

    @GET
    public Response streamExample(){
        StreamingOutput stream = new StreamingOutput() {
            @Override
            public void write(OutputStream out) throws IOException, WebApplicationException {
                Writer writer = new BufferedWriter(new OutputStreamWriter(out));
                for (int i = 0; i < 10000000 ; i++){
                    writer.write(i + " ");
                }
                writer.flush();
            }
        };
        return Response.ok(stream).build();
    }

}

Demo

URL: http://localhost:8081/jaxrs-streaming/api/orders

References

• StreamingOutput JavaDoc

Download