来自 Android 客户端的 HTTP 请求

Question

I have a really basic spring boot application running on localhost and i'm trying to get some data from another app on android studio. My endpoint looks like this: http://localhost:8080/company/ {id} and returns this:

In my android application, I have created a wrapper class:

package gr.games.panayiotis.myapplication;
import com.fasterxml.jackson.annotation.JsonProperty;

public class Company {

@JsonProperty("id")
private long id;
@JsonProperty("name")
private String name;


public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}
}

And inside main application i'm creating a new class called Task that extends AsyncTask to get the api:

package gr.games.panayiotis.myapplication;

import android.os.AsyncTask;
import android.os.Bundle;

import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.client.RestTemplate;

public class MainActivity extends AppCompatActivity {


public class Task extends AsyncTask<String, Void, ResponseEntity<Company>>{


    @Override
    protected ResponseEntity<Company> doInBackground(String... strings) {
        String url = strings[0];
        RestTemplate restTemplate = new RestTemplate();

        try{
            restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());


            HttpHeaders headers = new HttpHeaders();

            headers.add("Content-Type", "application/json");

            HttpEntity<String> entity = new HttpEntity<String>(headers);

            int id = 1;
            ResponseEntity<Company> responseEntity = restTemplate.exchange(url, HttpMethod.GET, entity, Company.class, id);

            System.out.println(responseEntity.getStatusCode());
            System.out.println(responseEntity.toString());

            return responseEntity;

        }catch (Exception e){
            //System.out.println("ERROR:\n");
            e.getMessage();
            //System.out.println("\nEND OF ERROR");
            return null;
        }
    }

    protected void onPostExecute(ResponseEntity<Company> response){
        //Company company = response.getBody();
       // System.out.println(company.getName());
    }
}


//A button invokes this method
public void getData(View view){
    String url = "http://localhost:8080/company/1";
    new Task().execute(url);
}



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

Inside the doInBackground() method my code runs up to the point where i call restTemplate.exchange(). After that it goes into the catch block and returns null to the response.

The first time i invoke my getData() method i get these warnings :

Capturing and displaying logcat messages from application. This behavior can be disabled in the 
"Logcat output" section of the "Debugger" settings page.
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
W/Java7Handlers: Unable to load JDK7 types (java.nio.file.Path): no Java7 type support added

I get no error but i can't figure out why i'm not getting a response. My Spring Boot application never gets a request. I just got into android so any help is much appreciated.

Answer 1

Add this line in your AndroidManifest.xml ,android:allowClearUserData="true".. maybe it will solve your issue.

 <application
    android:allowBackup="true"
    android:allowClearUserData="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">

or refer my methods from below link..

https://stackoverflow.com/questions/59464257/login-using-url-with-username-and-password-in-android-mobile-app/59466586#59466586

Answer 2

I found the error after some digging.

Turns out when you run your android application to an emulator the localhost address is this: http://10.0.2.2:8080 so all i had to do was change my url.