Created a context tool that loads up a message bundle of translation

strings and allows templates to reference those translated strings easily.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@83 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/webmacro/MsgTool.java

@@ -0,0 +1,131 @@
+//
+// $Id: MsgTool.java,v 1.1 2001/03/03 21:21:28 mdb Exp $
+
+package com.samskivert.webmacro;
+
+import java.text.MessageFormat;
+import java.util.MissingResourceException;
+import java.util.ResourceBundle;
+
+import org.webmacro.*;
+import org.webmacro.servlet.WebContext;
+import org.webmacro.util.PropertyObject;
+import org.webmacro.util.PropertyMethod;
+
+import com.samskivert.Log;
+
+/**
+ * The message tool maps a set of appliation messages (translation
+ * strings) into the context so that they are available to templates that
+ * wish to display localized text.
+ */
+public class MsgTool implements ContextTool
+{
+    /**
+     * Loads up the message resources and inserts them into the context.
+     */
+    public Object init (Context ctx)
+	throws InvalidContextException
+    {
+	try {
+	    WebContext wctx = (WebContext)ctx;
+
+	    // first fetch our messages resource bundle
+	    final ResourceBundle messages =
+		ResourceBundle.getBundle(MESSAGE_FILE_NAME);
+
+	    // then create a wrapper that allows webmacro to access it
+	    return new Wrapper(messages);
+
+	} catch (MissingResourceException mre) {
+	    Log.warning("Unable to load message bundle: " + mre);
+	    return new Wrapper(null);
+
+	} catch (ClassCastException cce) {
+	    throw new InvalidContextException("error.requires_webcontext");
+	}
+    }
+
+    public void destroy (Object obj)
+    {
+	// nothing to clean up
+    }
+
+    public static class Wrapper implements PropertyObject
+    {
+	public Wrapper (ResourceBundle bundle)
+	{
+	    _bundle = bundle;
+	}
+
+	public Object getProperty (Context context, Object[] names, int offset)
+	    throws PropertyException, SecurityException
+	{
+	    StringBuffer path = new StringBuffer();
+	    boolean bogus = false;
+	    int lastidx = names.length-1;
+
+	    // reconstruct the path to the property
+	    for (int i = offset; i < names.length; i++) {
+		// separate components with dots
+		if (path.length() > 0) {
+		    path.append(".");
+		}
+
+		// each name should either be a PropertyMethod or a string
+		// or an object that can be toString()ed
+		if (names[i] instanceof PropertyMethod) {
+		    // make a note to freak out if this is anything but
+		    // the last component of the path. we'd freak out now
+		    // but we want to reconstruct the path so that we can
+		    // report it in the exception that's thrown
+		    if (i != lastidx) {
+			bogus = true;
+		    }
+		    path.append(((PropertyMethod)names[i]).getName());
+
+		} else {
+		    path.append(names[i]);
+		}
+	    }
+
+	    // do any pending freaking out
+	    if (bogus) {
+		throw new PropertyException("Invalid message resource " +
+					    "path: " + path);
+	    }
+
+	    // look up the translated message
+	    String msg = _bundle.getString(path.toString());
+
+	    // if the last component is a property method, we want to
+	    // substitute it's arguments into the returned string using a
+	    // message formatter
+	    if (names[lastidx] instanceof PropertyMethod) {
+		PropertyMethod pm = (PropertyMethod)names[lastidx];
+		// we may cache message formatters later, but for now just
+		// use the static convenience function
+		Object[] args = pm.getArguments(context);
+		msg = MessageFormat.format(msg, args);
+	    }
+
+	    return msg;
+	}
+
+	public boolean setProperty (Context context, Object[] names, int offset,
+				    Object value)
+	    throws PropertyException, SecurityException
+	{
+	    throw new PropertyException("Setting a message resource " +
+					"is not supported!");
+	}
+
+	protected ResourceBundle _bundle;
+    }
+
+    /**
+     * The file name of the resource file that contains our translation
+     * strings.
+     */
+    protected static final String MESSAGE_FILE_NAME = "messages";
+}