Init project

src/main/java/ru/dmitriymx/vkapi/Browser.java

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+/*
+ * DmitriyMX <mail@dmitriymx.ru>
+ * 2017-04-10
+ */
+package ru.dmitriymx.vkapi;
+
+import java.io.IOException;
+
+public interface Browser {
+    Response get(String url) throws IOException;
+    Response post(String url, String data) throws IOException;
+}

src/main/java/ru/dmitriymx/vkapi/Response.java

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+/*
+ * DmitriyMX <mail@dmitriymx.ru>
+ * 2017-04-10
+ */
+package ru.dmitriymx.vkapi;
+
+public interface Response {
+    int getStatus();
+    String getContentType();
+    String getContent();
+}

src/main/java/ru/dmitriymx/vkapi/VkApi.java

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+/*
+ * DmitriyMX <mail@dmitriymx.ru>
+ * 2017-04-10
+ */
+package ru.dmitriymx.vkapi;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class VkApi {
+    private static final String VKAPI_URL = "https://api.vk.com/method/";
+    private final Logger logger = LoggerFactory.getLogger(VkApi.class);
+    private final String accessToken;
+    private final Browser browser;
+    private final Gson gson;
+    private String apiVersion = "5.62";
+    private long callPause = 1200L;
+    private long lastTime;
+    private int call = 0;
+
+    public VkApi(String accessToken, Browser browser) {
+        if (accessToken == null || accessToken.trim().isEmpty()) {
+            throw new RuntimeException("Access token don't be NULL or EMPTY!");
+        }
+        this.accessToken = accessToken;
+        this.browser = browser;
+        this.gson = new Gson();
+    }
+
+    public String getApiVersion() {
+        return apiVersion;
+    }
+
+    public void setApiVersion(String apiVersion) {
+        this.apiVersion = apiVersion;
+    }
+
+    public long getCallPause() {
+        return callPause;
+    }
+
+    public void setCallPause(long callPause) {
+        this.callPause = callPause;
+    }
+
+    public JsonObject execApi(String methodApi, Map<String, String> params) throws VkApiException {
+        checkCalls();
+        String url = VKAPI_URL + methodApi;
+        String postData = paramsToString(params);
+
+        Response response;
+        try {
+            response = browser.post(url, postData);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+
+        chechResponse(response);
+
+        JsonObject jsonObject = gson.fromJson(response.getContent(), JsonObject.class);
+        if (jsonObject.has("error")) {
+            throw new VkApiException(jsonObject);
+        }
+
+        return jsonObject;
+    }
+
+    public JsonObject longExecApi(String server, String key, long ts, long wait) throws VkApiException {
+        String url = String.format("https://%s?act=a_check&key=%s&ts=%d&wait=%d&mode=2&version=1",
+                server, key, ts, wait
+        );
+
+        Response response;
+        try {
+            response = browser.get(url);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+
+        chechResponse(response);
+
+        JsonObject jsonObject = gson.fromJson(response.getContent(), JsonObject.class);
+        if (jsonObject.has("error")) {
+            throw new VkApiException(jsonObject);
+        }
+
+        return jsonObject;
+    }
+
+    private String paramsToString(Map<String, String> params) {
+        String collect = "";
+        if (params != null && params.size() > 0) {
+            collect = "&" + params.entrySet().stream()
+                    .map(entry -> entry.getKey() + "=" + entry.getValue())
+                    .collect(Collectors.joining("&"));
+        }
+        return "access_token=" + accessToken + "&v=" + apiVersion + collect;
+    }
+
+    private void checkCalls() {
+        if (call >= 3) {
+            long currTime = System.currentTimeMillis();
+            long diff = currTime - lastTime;
+
+            if (diff <= callPause) {
+                safeSleep(callPause);
+            }
+
+            lastTime = System.currentTimeMillis();
+            call = 0;
+        } else {
+            safeSleep(callPause/3);
+            call++;
+        }
+    }
+
+    private void chechResponse(Response response) {
+        if (response.getStatus() != 200) {
+            throw new IllegalStateException(String.format("code != 200 (%d)", response.getStatus()));
+        }
+
+        if (!response.getContentType().equalsIgnoreCase("application/json") &&
+                !response.getContentType().equalsIgnoreCase("text/javascript")) {
+            throw new IllegalStateException(String.format("content type is not JSON/JavaScript (%s)", response.getContentType()));
+        }
+
+        if (response.getContent().isEmpty()) {
+            throw new IllegalStateException("content is empty");
+        }
+
+        if (logger.isDebugEnabled()) {
+            logger.debug(response.getContent());
+        }
+    }
+
+    private void safeSleep(long ms) {
+        try {
+            Thread.sleep(ms);
+        } catch (InterruptedException ignore) {
+            // ignore
+        }
+    }
+}

src/main/java/ru/dmitriymx/vkapi/VkApiException.java

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+/*
+ * DmitriyMX <mail@dmitriymx.ru>
+ * 2017-04-10
+ */
+package ru.dmitriymx.vkapi;
+
+import com.google.gson.JsonObject;
+
+public class VkApiException extends Exception {
+    public VkApiException(String message) {
+        super(message);
+    }
+
+    public VkApiException(JsonObject jsonObject) {
+        this(jsonObject.getAsJsonObject("error").get("error_msg").getAsString());
+    }
+}