Java tutorial
package org.apache.commons.digester3.examples.api.addressbook; /* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ import org.apache.commons.digester3.Digester; /** * A simple program to demonstrate the basic functionality of the * Commons Digester module. * <p> * This code will parse the provided "example.xml" file to build a tree * of java objects, then cause those objects to print out their values * to demonstrate that the input file has been processed correctly. * <p> * As with all code, there are many ways of achieving the same goal; * the solution here is only one possible solution to the problem. * <p> * Very verbose comments are included here, as this class is intended * as a tutorial; if you look closely at method "addRules", you will * see that the amount of code required to use the Digester is actually * quite low. * <p> * Usage: java Main example.xml */ public class Main { /** * Main method : entry point for running this example program. * <p> * Usage: java Example example.xml */ public static void main(String[] args) { if (args.length != 1) { usage(); System.exit(-1); } String filename = args[0]; // Create a Digester instance Digester d = new Digester(); // Prime the digester stack with an object for rules to // operate on. Note that it is quite common for "this" // to be the object pushed. AddressBook book = new AddressBook(); d.push(book); // Add rules to the digester that will be triggered while // parsing occurs. addRules(d); // Process the input file. try { java.io.File srcfile = new java.io.File(filename); d.parse(srcfile); } catch (java.io.IOException ioe) { System.out.println("Error reading input file:" + ioe.getMessage()); System.exit(-1); } catch (org.xml.sax.SAXException se) { System.out.println("Error parsing input file:" + se.getMessage()); System.exit(-1); } // Print out all the contents of the address book, as loaded from // the input file. book.print(); } private static void addRules(Digester d) { // -------------------------------------------------- // when we encounter a "person" tag, do the following: // create a new instance of class Person, and push that // object onto the digester stack of objects d.addObjectCreate("address-book/person", Person.class); // map *any* attributes on the tag to appropriate // setter-methods on the top object on the stack (the Person // instance created by the preceeding rule). // // For example: // if attribute "id" exists on the xml tag, and method setId // with one parameter exists on the object that is on top of // the digester object stack, then a call will be made to that // method. The value will be type-converted from string to // whatever type the target method declares (where possible), // using the commons ConvertUtils functionality. // // Attributes on the xml tag for which no setter methods exist // on the top object on the stack are just ignored. d.addSetProperties("address-book/person"); // call the addPerson method on the second-to-top object on // the stack (the AddressBook object), passing the top object // on the stack (the recently created Person object). d.addSetNext("address-book/person", "addPerson"); // -------------------------------------------------- // when we encounter a "name" tag, call setName on the top // object on the stack, passing the text contained within the // body of that name element [specifying a zero parameter count // implies one actual parameter, being the body text]. // The top object on the stack will be a person object, because // the pattern address-book/person always triggers the // ObjectCreateRule we added previously. d.addCallMethod("address-book/person/name", "setName", 0); // -------------------------------------------------- // when we encounter an "email" tag, call addEmail on the top // object on the stack, passing two parameters: the "type" // attribute, and the text within the tag body. d.addCallMethod("address-book/person/email", "addEmail", 2); d.addCallParam("address-book/person/email", 0, "type"); d.addCallParam("address-book/person/email", 1); // -------------------------------------------------- // When we encounter an "address" tag, create an instance of class // Address and push it on the digester stack of objects. After // doing that, call addAddress on the second-to-top object on the // digester stack (a "Person" object), passing the top object on // the digester stack (the "Address" object). And also set things // up so that for each child xml element encountered between the start // of the address tag and the end of the address tag, the text // contained in that element is passed to a setXXX method on the // Address object where XXX is the name of the xml element found. d.addObjectCreate("address-book/person/address", Address.class); d.addSetNext("address-book/person/address", "addAddress"); d.addSetNestedProperties("address-book/person/address"); } private static void usage() { System.out.println("Usage: java Main example.xml"); } }