android http json

使用Gson库

Step1: download Gson jar file

goto https://github.com/google/gson

Gson Download downloads at Maven Central

step2: To use Gson in Android

1) copy jar to app\libs （物理方式复制进入）

2) app->build.gradle文件中添加

dependencies {
implementation 'com.google.code.gson:gson:2.8.5'
}

ps:  错误处理

错误1：不能导入

ps: 点击alt+enter import class 无效时，点击alt+enter弹出菜单中gradle sync

错误2： Program type already present: com.google.gson.FieldNamingStrategy

dependencies {

configurations {
all*.exclude group: 'com.google.code.gson'
}

step 3 : 使用HttpURLConnection + Gson 示例

package com.qtechnix.hellowordl2;

import android.util.Log;
import com.google.gson.Gson;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;

public class HttpJson {

    public void HttpJson() {

    }

    public String convertStreamToString(InputStream is) {
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();
        String line = null;
        try {
            while ((line = reader.readLine()) != null) {
                sb.append(line + "/n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return sb.toString();
    }

    public Map<String, String> execute(String urlStr, String method, String... params) {
        InputStream inputStream = null;
        HttpURLConnection urlConnection = null;

        try {

            String domain = "";
            String member_req_token_url = "";
            // read responseURLEncoder.encode(para, "GBK");
            String urlWithParams = domain + member_req_token_url + "?userName=" + java.net.URLEncoder.encode(params[0], "utf-8") + "&password=" + params[1];

            URL url = new URL(urlStr);//urlWithParams);
            urlConnection = (HttpURLConnection) url.openConnection();

            //optional request header
            urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8");

            //optional request header
            urlConnection.setRequestProperty("Accept", "application/json");

            // for Get request
            urlConnection.setRequestMethod(method);//"GET" | "POST";
            int statusCode = urlConnection.getResponseCode();

            // 200 represents HTTP OK
            if (statusCode == 200) {
                inputStream = new BufferedInputStream(urlConnection.getInputStream());
                String response = convertStreamToString(inputStream);
                Gson gson = new Gson();
                Map<String, String> resultMap = gson.fromJson(response, Map.class);
                if (resultMap != null && resultMap.size() > 0) {
                    Log.i("gmx", "please check the map with key");
                }
                return resultMap;
                //UserDto dto = gson.fromJson(response, UserDto.class);
                //if (dto != null && dto.getToken() != null) {
                //   Log.i("token", "find the token = " + dto.getToken());
                //}
                //return dto;
            }
            else {

            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
        }
        return null;
    }

    public Map<String, String> execute(String urlStr, String method, Map<String, String> dto) {
        InputStream inputStream = null;
        HttpURLConnection urlConnection = null;
        try {
            URL url = new URL(urlStr);
            urlConnection = (HttpURLConnection) url.openConnection();

            // optional request header
            urlConnection.setRequestProperty("Content-Type", "application/json; charset=UTF-8");

            // optional request header
            urlConnection.setRequestProperty("Accept", "application/json");

            //dto.setCreator(java.net.URLEncoder.encode(dto.getCreator(), "utf-8"));

            // for Get request
            urlConnection.setRequestMethod(method);//"POST");
            urlConnection.setDoOutput(true);
            DataOutputStream wr = new DataOutputStream(urlConnection.getOutputStream());
            Gson gson = new Gson();
            String jsonString = gson.toJson(dto);
            wr.writeBytes(jsonString);
            wr.flush();
            wr.close();
            // try to get response
            int statusCode = urlConnection.getResponseCode();
            if (statusCode == 200) {
                inputStream = new BufferedInputStream(urlConnection.getInputStream());
                String response = convertStreamToString(inputStream);
                Map<String, String> resultMap = gson.fromJson(response, Map.class);
                if (resultMap != null && resultMap.size() > 0) {
                    Log.i("applyDesigner", "please check the map with key");
                }
                return resultMap;
            }
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        finally
        {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
        }
        return null;
    }
}

错误3:运行异常 at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork
原因：Android 3.0之后不运行主线程访问网络，需另起线程访问。