Support for UserDefinedValue can be fetched from configured json DataSource

build.gradle

@@ -34,6 +34,8 @@ dependencies {
     compile "org.parboiled:parboiled-java:$parboiledJavaVersion"
     compile "org.yaml:snakeyaml:$snakeyamlVersion"
     compile "org.apache.commons:commons-csv:$commonsCsvVersion"
+    compile "com.googlecode.json-simple:json-simple:$gsonVersion"
+    compile "com.jayway.jsonpath:json-path:$jsonPathVersion"
 
     testCompile "junit:junit:$junitVersion"
     testCompile "org.spockframework:spock-core:$spockCoreVersion"

gradle.properties

@@ -12,3 +12,5 @@ junitVersion=4.12
 spockCoreVersion=1.0-groovy-2.4
 cglibNodepVersion=3.2.0
 groovyAllVersion=2.4.3
+gsonVersion=1.1
+jsonPathVersion=2.3.0

src/main/java/io/smartcat/ranger/core/UserDefinedValue.java

@@ -0,0 +1,159 @@
+package io.smartcat.ranger.core;
+
+import com.jayway.jsonpath.JsonPath;
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * @author hkilari
+ *
+ *         UserDefined Value Implementation to allow Berserker User define a Custom Value in
+ *         berserker ranger configuration. The Custom Value will be retrieved from the data source
+ *         configured by User based on his query config
+ *
+ */
+public class UserDefinedValue extends Value<String> {
+
+  private Value<String> jsonName;
+  private Value<String> filter;
+  private Value<String> regExpression;
+  private List<String> finalContent;
+  private long contentlastUpdationTime;
+  private Value<String> refreshInterval;
+  private Value<String> defaultRefreshInterval = new Value<String>() {
+  };
+
+  /**
+   * Constructor for UserDefinedValue.
+   *
+   * @param regExpression
+   *          To support the case where the requirement is not complete field and only specific
+   *          part.
+   * @param refreshInterval
+   *          To refresh the data at configured intervals if the source support dynamic data
+   *          retrieval.
+   * @param filter
+   *          JSON path query to extract a Filed from specified Data Source. For semantics, please
+   *          refer to https://github.com/json-path/JsonPath.
+   * @param jsonName
+   *          Can be a name of JSON file available in classpath/ A Rest endpoint that return a JSON
+   *          response.
+   */
+  public UserDefinedValue(Value<String> regExpression, Value<String> refreshInterval,
+      Value<String> filter, Value<String> jsonName) {
+    defaultRefreshInterval.val = "600";
+    if (jsonName == null) {
+      throw new IllegalArgumentException("datasource cannot be null.");
+    }
+    this.jsonName = jsonName;
+    this.filter = filter;
+    this.regExpression = regExpression;
+    this.refreshInterval = refreshInterval == null ? defaultRefreshInterval : refreshInterval;
+    this.finalContent = new ArrayList<>();
+  }
+
+  @Override
+  public void reset() {
+    jsonName.reset();
+    filter.reset();
+    regExpression.reset();
+    refreshInterval.reset();
+    super.reset();
+
+  }
+
+  @Override
+  protected void eval() {
+    if (isContentExpired()) {
+      getDataFromJson();
+    }
+    val = getRandomValue();
+  }
+
+  private boolean isContentExpired() {
+    // Checks if the finalContent to be refreshed based on used defined refreshInterval.
+    if (System.currentTimeMillis() - contentlastUpdationTime > Long.parseLong(refreshInterval.val)
+        * 1000) {
+      return true;
+    }
+    return false;
+  }
+
+  private String getRandomValue() {
+    if (finalContent != null && !finalContent.isEmpty())
+      return extractField(finalContent.get(new Random().nextInt(finalContent.size())).toString(),
+          regExpression.get());
+    else
+      return "";
+  }
+
+  private void getDataFromJson() {
+    try {
+      // check If Source is a http service
+      if (jsonName.get().contains("http")) {
+        getDataFromHttpRequest();
+      } else {
+        // Source treated as a local json file
+        InputStream in = Thread.currentThread().getContextClassLoader()
+            .getResourceAsStream(jsonName.get() + ".json");
+        if (in == null) {
+          in = new FileInputStream(jsonName.get() + ".json");
+        }
+        if (in != null) {
+          finalContent = JsonPath.read(in, filter.get());
+        }
+      }
+    } catch (Exception e) {
+      e.printStackTrace();
+    }
+  }
+
+  /**
+   * Retrieves data from a http service endpoint.
+   */
+  private void getDataFromHttpRequest() {
+    try {
+      InputStream in;
+      URL obj = new URL(jsonName.val);
+      HttpURLConnection con = (HttpURLConnection) obj.openConnection();
+      con.setRequestMethod("GET");
+      con.setRequestProperty("accept", "application/json");
+      int responseCode = con.getResponseCode();
+      if (responseCode == HttpURLConnection.HTTP_OK) { // success
+        in = con.getInputStream();
+        finalContent = JsonPath.read(in, filter.get());
+        in.close();
+        contentlastUpdationTime = System.currentTimeMillis();
+      } else {
+        System.out.println("GET request not worked");
+      }
+    } catch (Exception e) {
+      e.printStackTrace();
+    }
+  }
+
+  /**
+   * @param latestCommandOutput
+   * @param regExpression
+   * @return
+   */
+  private String extractField(String inputString, String regExpression) {
+    if (regExpression != null && !"".equals(regExpression.trim())) {
+      Pattern p = Pattern.compile(regExpression);
+      Matcher m = p.matcher(inputString);
+      if (m.find()) {
+        if (m.groupCount() > 0)
+          return m.group(1);
+      }
+      return null;
+    }
+    return inputString;
+  }
+}