add a useful utilities function (with test)

SVN: 1259

common/source/java/ch/systemsx/cisd/common/config/ConfigUtilities.java

+/*
+ * Copyright 2007 ETH Zuerich, CISD
+ *
+ * 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 ch.systemsx.cisd.common.config;
+
+import java.util.Properties;
+import java.util.Set;
+
+/**
+ * Useful utility functions concerning configuration data. 
+ *
+ * @author Franz-Josef Elmer
+ */
+public class ConfigUtilities
+{
+    /**
+     * Extracts from the specified properties object all properties starting with the specified key prefix.
+     */
+    public static Properties extractPropertiesStartingWith(String prefix, Properties properties)
+    {
+        assert prefix != null : "Missing prefix";
+        assert properties != null : "Missing properties";
+        
+        Properties result = new Properties();
+        int prefixLength = prefix.length();
+        Set<Object> keys = properties.keySet();
+        for (Object object : keys)
+        {
+            String key = object.toString();
+            if (key.startsWith(prefix))
+            {
+                result.setProperty(key.substring(prefixLength), properties.getProperty(key));
+            }
+        }
+        return result;
+    }
+    
+    private ConfigUtilities()
+    {
+    }
+    
+}

common/sourceTest/java/ch/systemsx/cisd/common/config/ConfigUtilitiesTest.java

+/*
+ * Copyright 2007 ETH Zuerich, CISD
+ *
+ * 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 ch.systemsx.cisd.common.config;
+
+import static org.testng.AssertJUnit.assertEquals;
+
+import java.util.Properties;
+
+import org.testng.annotations.Test;
+
+/**
+ * 
+ *
+ * @author Franz-Josef Elmer
+ */
+public class ConfigUtilitiesTest
+{
+    @Test
+    public void testEmptyProperties()
+    {
+        Properties props = ConfigUtilities.extractPropertiesStartingWith("blabla", new Properties());
+        assertEquals(0, props.size());
+    }
+    
+    @Test
+    public void testNonEmptyInputPropertiesButEmptyResult()
+    {
+        Properties properties = new Properties();
+        properties.setProperty("bla", "blub");
+        Properties props = ConfigUtilities.extractPropertiesStartingWith("blabla", properties);
+        assertEquals(0, props.size());
+    }
+    
+    @Test
+    public void testNonEmptyInputPropertiesAndNonEmptyResult()
+    {
+        Properties properties = new Properties();
+        properties.setProperty("hello", "world");
+        properties.setProperty("bla", "bla");
+        properties.setProperty("bla.", "blub");
+        properties.setProperty("bla.a", "blab");
+        properties.setProperty("bla.ab", "blab ab");
+        Properties props = ConfigUtilities.extractPropertiesStartingWith("bla.", properties);
+        assertEquals(3, props.size());
+        assertEquals("blub", props.getProperty(""));
+        assertEquals("blab", props.getProperty("a"));
+        assertEquals("blab ab", props.getProperty("ab"));
+    }
+}