adding changes for the grant type client credentials mechanism

src/main/java/io/cdap/plugin/http/source/common/BaseHttpSourceConfig.java

@@ -28,10 +28,7 @@
 import io.cdap.plugin.http.source.common.error.ErrorHandling;
 import io.cdap.plugin.http.source.common.error.HttpErrorHandlerEntity;
 import io.cdap.plugin.http.source.common.error.RetryableErrorHandling;
-import io.cdap.plugin.http.source.common.http.AuthType;
-import io.cdap.plugin.http.source.common.http.HttpClient;
-import io.cdap.plugin.http.source.common.http.KeyStoreType;
-import io.cdap.plugin.http.source.common.http.OAuthUtil;
+import io.cdap.plugin.http.source.common.http.*;
 import io.cdap.plugin.http.source.common.pagination.PaginationIteratorFactory;
 import io.cdap.plugin.http.source.common.pagination.PaginationType;
 import io.cdap.plugin.http.source.common.pagination.page.PageFormat;
@@ -119,6 +116,13 @@ public abstract class BaseHttpSourceConfig extends ReferencePluginConfig {
   public static final String PAGINATION_INDEX_PLACEHOLDER_REGEX = "\\{pagination.index\\}";
   public static final String PAGINATION_INDEX_PLACEHOLDER = "{pagination.index}";
   public static final String PROPERTY_GRANT_TYPE = "grantType";
+  public static final String PROPERTY_GRANT_TYPE_LABEL = "Grant type";
+
+  public static final String PARAMETER_CLIENT_ID = "client_id";
+  public static final String PARAMETER_CLIENT_SECRET = "client_secret";
+  public static final String PARAMETER_REFRESH_TOKEN = "refresh_token";
+  public static final String PARAMETER_GRANT_TYPE = "grant_type";
+  public static final String PARAMETER_ACCESS_TOKEN = "access_token";
 
   @Name(PROPERTY_URL)
   @Description("Url to fetch to the first page. The url must start with a protocol (e.g. http://).")
@@ -961,8 +965,10 @@ PAGINATION_INDEX_PLACEHOLDER, getPaginationType()),
   }
 
   private boolean refreshTokenGrantType() {
-    if (getGrantType() == "refresh_token") {
+    if (getGrantType() == GrantType.REFRESH_TOKEN.getValue()) {
       return true;
+    } else if (getGrantType() == GrantType.CLIENT_CREDENTIALS.getValue()) {
+      return false;
     }
     return false;
   }

src/main/java/io/cdap/plugin/http/source/common/http/GrantType.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright © 2022 Cask Data, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package io.cdap.plugin.http.source.common.http;
+
+import io.cdap.plugin.http.source.common.BaseHttpSourceConfig;
+import io.cdap.plugin.http.source.common.exceptions.InvalidPropertyTypeException;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Enum for different grant type methods.
+ */
+public enum GrantType {
+  REFRESH_TOKEN("refresh_token"),
+  CLIENT_CREDENTIALS("client_credentials");
+
+  private final String value;
+
+  GrantType(String value) {
+    this.value = value;
+  }
+
+  public String getValue() {
+    return value;
+  }
+
+  /**
+   * Returns the GrantType.
+   *
+   * @param value the value is string type.
+   * @return The GrantType
+   */
+  public static GrantType fromValue(String value) {
+    return Arrays.stream(GrantType.values()).filter(grantType -> grantType.getValue().equals(value))
+      .findAny().orElseThrow(() -> new InvalidPropertyTypeException(BaseHttpSourceConfig.PROPERTY_GRANT_TYPE_LABEL,
+                                                                    value, getAllowedValues()));
+  }
+
+  public static List<String> getAllowedValues() {
+    return Arrays.stream(GrantType.values()).map(v -> v.getValue())
+      .collect(Collectors.toList());
+  }
+}

src/main/java/io/cdap/plugin/http/source/common/http/HttpClient.java

@@ -136,12 +136,12 @@ private CloseableHttpClient createHttpClient() throws IOException {
 
     switch (authType) {
       case OAUTH2:
-        String accessToken;
-        if (config.getGrantType() == "refresh_token") {
+        String accessToken = null;
+        if (config.getGrantType() == GrantType.REFRESH_TOKEN.getValue()) {
           accessToken = OAuthUtil.getAccessTokenByRefreshToken(HttpClients.createDefault(), config.getTokenUrl(),
                   config.getClientId(), config.getClientSecret(),
                   config.getRefreshToken(), config.getGrantType());
-        } else {
+        } else if (config.getGrantType() == GrantType.CLIENT_CREDENTIALS.getValue()) {
           accessToken = OAuthUtil.getAccessTokenByClientCredentials(HttpClients.createDefault(), config.getTokenUrl(),
                   config.getClientId(), config.getClientSecret(), config.getGrantType());
         }

src/main/java/io/cdap/plugin/http/source/common/http/OAuthUtil.java

@@ -48,10 +48,10 @@ public static String getAccessTokenByRefreshToken(CloseableHttpClient httpclient
     URI uri;
     try {
       uri = new URIBuilder(tokenUrl)
-        .setParameter("client_id", clientId)
-        .setParameter("client_secret", clientSecret)
-        .setParameter("refresh_token", refreshToken)
-        .setParameter("grant_type", grantType)
+        .setParameter(BaseHttpSourceConfig.PARAMETER_CLIENT_ID, clientId)
+        .setParameter(BaseHttpSourceConfig.PARAMETER_CLIENT_SECRET, clientSecret)
+        .setParameter(BaseHttpSourceConfig.PARAMETER_REFRESH_TOKEN, refreshToken)
+        .setParameter(BaseHttpSourceConfig.PARAMETER_GRANT_TYPE, grantType)
         .build();
     } catch (URISyntaxException e) {
       throw new IllegalArgumentException("Failed to build token URI for OAuth2", e);
@@ -61,7 +61,7 @@ public static String getAccessTokenByRefreshToken(CloseableHttpClient httpclient
     CloseableHttpResponse response = httpclient.execute(httppost);
     String responseString = EntityUtils.toString(response.getEntity(), "UTF-8");
 
-    JsonElement jsonElement = JSONUtil.toJsonObject(responseString).get("access_token");
+    JsonElement jsonElement = JSONUtil.toJsonObject(responseString).get(BaseHttpSourceConfig.PARAMETER_ACCESS_TOKEN);
     if (jsonElement == null) {
          throw new IllegalArgumentException("Access token not found");
     }
@@ -103,7 +103,7 @@ public static String getAccessTokenByClientCredentials(CloseableHttpClient httpc
           throws IOException {
     URI uri;
     try {
-      uri = new URIBuilder(tokenUrl).setParameter("grant_type", grantType).build();
+      uri = new URIBuilder(tokenUrl).setParameter(BaseHttpSourceConfig.PARAMETER_GRANT_TYPE, grantType).build();
     } catch (URISyntaxException e) {
       throw new IllegalArgumentException("Failed to build token URI for OAuth2", e);
     }
@@ -114,7 +114,7 @@ public static String getAccessTokenByClientCredentials(CloseableHttpClient httpc
     CloseableHttpResponse response = httpclient.execute(httppost);
     String responseString = EntityUtils.toString(response.getEntity(), "UTF-8");
 
-    JsonElement jsonElement = JSONUtil.toJsonObject(responseString).get("access_token");
+    JsonElement jsonElement = JSONUtil.toJsonObject(responseString).get(BaseHttpSourceConfig.PARAMETER_ACCESS_TOKEN);
     return jsonElement.getAsString();
   }
 

widgets/HTTP-batchsource.json

@@ -696,19 +696,16 @@
       },
       "show": [
         {
-          "widget-type": "textbox",
-          "label": "Token URL",
-          "name": "tokenUrl"
+          "name": "tokenUrl",
+          "type": "property"
         },
         {
-          "widget-type": "textbox",
-          "label": "Client ID",
-          "name": "clientId"
+          "name": "clientId",
+          "type": "property"
         },
         {
-          "widget-type": "password",
-          "label": "Client Secret",
-          "name": "clientSecret"
+          "name": "clientSecret",
+          "type": "property"
         },
         {
           "name": "scopes",
@@ -799,9 +796,8 @@
       },
       "show": [
         {
-          "widget-type": "textbox",
-          "label": "Auth URL",
-          "name": "authUrl"
+          "name": "authUrl",
+          "type": "property"
         },
         {
           "name": "refreshToken",