Downloading Images from Spring Boot REST APIs

Spring Boot applications often need to provide some REST APIs to allow front-end applications to download images. We will introduce 2 different implementations. One is that when open the image URL is opened with a browser, the image will be downloaded into a file. The other is that the browser will directly display the image.

Downloading Images as Files

If you want users to download the image directly into a file when clicking on the image URL on the front-end page, you can refer to the following method:

• • Spring Boot

Downloading Files from Spring Boot REST APIs

• ByWayne
• 10/09/2020

Displaying Images on Browsers

If you want images are displayed on browsers directly, you can use the follow method.

Create ImageResourceHttpRequestHandlerand inheritance ResourceHttpRequestHandler, the code is as follows:

import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.resource.ResourceHttpRequestHandler;

import javax.servlet.http.HttpServletRequest;
import java.io.File;

@Component
public class ImageResourceHttpRequestHandler extends ResourceHttpRequestHandler {
    public static final String ATTRIBUTE_FILE = "DOWNLOADING_FILE";

    @Override
    protected Resource getResource(HttpServletRequest request) {
        File file = (File) request.getAttribute(ATTRIBUTE_FILE);
        return new FileSystemResource(file);
    }
}

Create a controller to receive requests, and then let ImageResourceHttpRequestHandler handle the request.

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;

@RestController
@RequestMapping("/images")
public class ImageController {
    @Resource
    private ImageResourceHttpRequestHandler imageResourceHttpRequestHandler;

    @GetMapping("/download")
    public void download(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
            throws ServletException, IOException {
        File file = new File("/path/to/image.jpg");
        httpServletRequest.setAttribute(ImageResourceHttpRequestHandler.ATTRIBUTE_FILE, file);
        imageResourceHttpRequestHandler.handleRequest(httpServletRequest, httpServletResponse);
    }
}

Open http://localhost:8080/images/download with a browser, and the image will be displayed directly on the browser.