Created a class for properties related utility functions. Created a

function that extracts sub-properties from a global properties file.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@11 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/util/Makefile

@@ -1,9 +1,10 @@
 #
-# $Id: Makefile,v 1.1 2000/10/31 00:04:15 mdb Exp $
+# $Id: Makefile,v 1.2 2000/10/31 00:48:13 mdb Exp $
 
 ROOT = ../../..
 
 SRCS = \
+	PropertiesUtil.java \
 	StringUtil.java \
 
 include $(ROOT)/build/Makefile.java

projects/samskivert/src/java/com/samskivert/util/PropertiesUtil.java

@@ -0,0 +1,70 @@
+//
+// $Id: PropertiesUtil.java,v 1.1 2000/10/31 00:48:13 mdb Exp $
+
+package com.samskivert.util;
+
+import java.util.Enumeration;
+import java.util.Properties;
+
+/**
+ * Utility functions related to properties objects.
+ */
+public class PropertiesUtil
+{
+    /**
+     * Extracts all properties from the supplied properties object with
+     * the specified prefix, removes the prefix from the key for those
+     * properties and inserts them into a new properties object which is
+     * then returned. This is useful for extracting properties from a
+     * global configuration object that must be passed to a service that
+     * expects it's own private properties (JDBC for example).
+     *
+     * The property file might look like so:
+     *
+     * <pre>
+     * my_happy_param=my_happy_value
+     * ...
+     * jdbc.driver=foo.bar.Driver
+     * jdbc.url=jdbc://blahblah
+     * jdbc.username=bob
+     * jdbc.password=is your uncle
+     * ...
+     * my_happy_other_param=my_happy_other_value
+     * </pre>
+     *
+     * This can be supplied to <code>getSubProperties()</code> with a
+     * prefix of <code>"jdbc"</code> and the following properties would be
+     * returned:
+     *
+     * <pre>
+     * driver=foo.bar.Driver
+     * url=jdbc://blahblah
+     * username=bob
+     * password=is your uncle
+     * </pre>
+     */
+    public Properties getSubProperties (Properties source, String prefix)
+    {
+	Properties dest = new Properties();
+
+	// extend the prefix to contain a dot
+	prefix = prefix + ".";
+	int preflen = prefix.length();
+
+	// scan the source properties
+	Enumeration names = source.propertyNames();
+	while (names.hasMoreElements()) {
+	    String name = (String)names.nextElement();
+
+	    // skip unrelated properties
+	    if (!name.startsWith(prefix)) {
+		continue;
+	    }
+
+	    // insert the value into the new properties minus the prefix
+	    dest.put(name.substring(preflen), source.getProperty(name));
+	}
+
+	return dest;
+    }
+}