如何使Spring REST API使用者

Question

I am new to spring``REST api design. Somehow I have created a api (producer). Now I want to consume this same API . I have never consumed API before. How can I do so ? I have tried using HttpURLConnection but couldn't do it. Below is my code for producer api. Now I want to call this API using java code.

Rest Api (producer)

@PostMapping(value="register")
    public ResponseEntity<CoreResponseHandler> doRegister(@RequestPart String json,@RequestParam(required=false) MultipartFile file)  throws JsonParseException, JsonMappingException, IOException {    
        try {

            String imgPath = env.getProperty("image_path");

            String outputDir = imgPath; 

            RegEntity reg = new ObjectMapper().readValue(json, RegEntity.class);

            String  result = validateInsertRegBean(reg);
            if(!result.equalsIgnoreCase("success")) {
                return new ResponseEntity<CoreResponseHandler>(new SuccessResponseBeanRefined(HttpStatus.BAD_REQUEST, ResponseStatusEnum.FAILED, ApplicationResponse.Failed,result),HttpStatus.BAD_REQUEST);

            }
            String imagePath=null;
            System.out.println("=================================");
            if(file!=null && !file.isEmpty()) {
                System.out.println("file NOT nOT NOT EmpTY");
            String username=reg.getUsername();
            File userFile = new File(outputDir+username);
            if(!userFile.exists()) {
                userFile.mkdir();
            }

            try {
                file.transferTo(new File(outputDir+username+File.separator+ file.getOriginalFilename()));
                System.out.println("***************   "+file.getOriginalFilename());
            } catch (IOException e) {
                return new ResponseEntity<CoreResponseHandler>(new SuccessResponseBeanRefined(HttpStatus.BAD_REQUEST, ResponseStatusEnum.FAILED, ApplicationResponse.Failed,"image unable to upload"),HttpStatus.BAD_REQUEST);
            }


            File ff[] = userFile.listFiles();
            for(File f:ff) {
                if(f.getName().contains("thumbnail"))
                    f.delete();
            }


            Thumbnails.of(new File(outputDir+username+File.separator).listFiles())
            .size(100, 100)
            .outputFormat("jpg")
            .toFiles(Rename.SUFFIX_HYPHEN_THUMBNAIL);

            imagePath=outputDir+username+File.separator+file.getOriginalFilename();

            }
            Date dt = new Date();
            long lngDt = dt.getTime();
            Ofuser ofuser = new Ofuser();
            ofuser.setBlockedNum(null);
            ofuser.setEmail(reg.getEmail());
            ofuser.setEncryptedPassword(reg.getEncryptedPassword());
            ofuser.setName(reg.getName());
            ofuser.setStatus(reg.getStatus());
            ofuser.setUsername(reg.getUsername());
            ofuser.setVcardResize(null);
            ofuser.setImage(null);
            ofuser.setPlainPassword(null);
            ofuser.setCreationDate(lngDt+"");
            ofuser.setModificationDate(lngDt+"");
            ofuser.setImagePath(imagePath);
            Ofuser tempuser = ofuserService.save(ofuser);
            IdMaster idMaster0 = new IdMaster();
            idMaster0.setUsername(tempuser.getUsername());
            idMaster0.setUserId(lngDt+"");
            IdMaster tempidMaster = idMasterService.save(idMaster0);
            if(tempuser!=null && tempidMaster!=null) {
                System.out.println("################## "+tempuser.getUsername());
                return new ResponseEntity<CoreResponseHandler>(
                        new SuccessResponseBean(HttpStatus.OK, ResponseStatusEnum.SUCCESSFUL, ApplicationResponse.SUCCESSFUL),
                        HttpStatus.OK);
            }
            else {
                return new ResponseEntity<CoreResponseHandler>(
                        new SuccessResponseBean(HttpStatus.BAD_REQUEST, ResponseStatusEnum.FAILED, ApplicationResponse.Failed),
                        HttpStatus.BAD_REQUEST);
            }

        }catch(Exception ex) {
            ex.printStackTrace();
            return new ResponseEntity<CoreResponseHandler>(new SuccessResponseBeanRefined(HttpStatus.BAD_REQUEST, ResponseStatusEnum.FAILED, ApplicationResponse.Failed,"something went wrong!!"),HttpStatus.BAD_REQUEST);

        }
    }

postman screenshot

On postman its working fine. Now I want to consume this very api programatically. how can I do this. Basically I need to call this method using some code:

 @PostMapping(value="register")
        public ResponseEntity<CoreResponseHandler> doRegister(@RequestPart String json,@RequestParam(required=false) MultipartFile file){}

don't have much experience in doing so..please guide.

============================================================================

Ok, after much digging in google I made following code but still not able to call rest api. My code:

package com.google.reg.utils;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import org.json.JSONException;
import org.json.JSONObject;
public class Test {
    public static void main(String[] args) {
        try {
            URL url = new URL("http://localhost:8012/register");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW charset=utf-8");
            conn.setDoOutput(true);
            conn.setDoInput(true);
            JSONObject jsonObject = buidJsonObject();
            setPostRequestContent(conn, jsonObject);
            conn.connect();
            System.out.println(conn.getResponseCode());
            if(conn.getResponseCode()==200){
                BufferedReader reader= new BufferedReader(new InputStreamReader(conn.getInputStream()));
                StringBuilder stringBuilder = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null)
                {
                    stringBuilder.append(line + "\n");
                }
                System.out.println(stringBuilder+" <<<<<<<<<<<<<<<<<<<<<<<<<" );
                jsonObject=new JSONObject(stringBuilder.toString());    
            }
            else{
                BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getErrorStream()));
                StringBuilder stringBuilder = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null)
                {
                    stringBuilder.append(line + "\n");
                }
                System.out.println(stringBuilder+" <<<<<<<<<<<<<<<<<<<<<<<<<" );
                System.out.println("ERRORERRORERRORERRORERRORERRORERRORERRORERROR"+conn.getResponseCode());
            }

        }catch(Exception ex) {
            ex.printStackTrace();
        }

    }

    private static  JSONObject buidJsonObject() throws JSONException {

        JSONObject jsonObject = new JSONObject();
        jsonObject.accumulate("username", "129898912");
        jsonObject.accumulate("encryptedPassword", "encpass");
        jsonObject.accumulate("name",  "fish");
        jsonObject.accumulate("email",  "fish@fish.com");
        jsonObject.accumulate("status",  "active");


        return jsonObject;
    }

    private static void setPostRequestContent(HttpURLConnection conn, 
            JSONObject jsonObject) throws IOException {

        OutputStream os = conn.getOutputStream();
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
        writer.write(jsonObject.toString());
        writer.flush();
        writer.close();
        os.close();
    }

}

but still no success. Below is the error I get in console:

400
<html><body><h1>Whitelabel Error Page</h1><p>This application has no explicit mapping for /error, so you are seeing this as a fallback.</p><div id='created'>Wed Sep 26 12:28:17 UTC 2018</div><div>There was an unexpected error (type=Bad Request, status=400).</div><div>Required request part &#39;json&#39; is not present</div></body></html>
 <<<<<<<<<<<<<<<<<<<<<<<<<
ERRORERRORERRORERRORERRORERRORERRORERRORERROR400

Answer 1

Since you are using Spring, you can use RestTemplate which is again a spring library. Please refer rest template

This is actually one client, but there are more. Its up to you do decide which one you should use and which suites best to you.

Answer 2

As @Damith said, rest template is a good library, and it's embedded on the springboot dependency tree. But also there are some others library, such as OkHttp or JAX-RX which can help you. My favorite one is OkHttp3, Good Luck.