"person.username.firstname"类型参数字符串自动组装成对象的原理
在使用Struts2、WebWork框架开发Web应用时，JSP页中的表单项，常常会使用这样的参数名：
<input type="text" name="person.username" /><input type="password" name="person.password" />
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甚至，可以有更多层次的，如：
<input type="text" name="person.username.firstname" /><input type="text" name="person.username.lastname" />
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上面第一例，在后端Java代码中，自然有一个Person类与之对应。其中，这个Person类包含2个属性:username, password，还有必要的Setter和Getter方法。
上面第二例，同样有一个Person类与之相对应，而Person类中包括了一个Username类型的属性"username"；而在Username类里，有firstname和lastname两个属性。同样，相应的Setter和Getter方法是必不可少的。
那么，那些框架是怎么自动将型如"person.username.firstname"的字符串，组装成相应的对象(如Person对象)的呢？
请看以下代码：
/* * Copyright (c) 2002-2003 by OpenSymphony * All rights reserved. */package com.opensymphony.provider.bean;import com.opensymphony.provider.BeanProvider;import com.opensymphony.provider.ProviderConfigurationException;import java.beans.PropertyDescriptor;import java.lang.reflect.Field;import java.lang.reflect.Method;import java.util.StringTokenizer;/** * BeanProvider implementation for accessing properties. * * Can handle a.b.c.d -> getA().getB().getC().getD(). * Access properties in this order: bean.getA(), bean.isA(), bean.a(), bean.a. * * Can also deal with setter methods. * * @author <a href="mailto:joe@truemesh.com">Joe Walnes</a> * @version $Revision: 1.1.1.1 $ */public class DefaultBeanProvider implements BeanProvider { //~ Static fields/initializers ///////////////////////////////////////////// private static String GET = "get"; private static String SET = "set"; private static String IS = "is"; //~ Methods //////////////////////////////////////////////////////////////// public boolean setProperty(Object object, String property, Object value) { if ((property == null) || (object == null)) { return false; } // Split out property on dots ( "person.name.first" -> "person","name","first" -> getPerson().getName().getFirst() ) StringTokenizer st = new StringTokenizer(property, "."); if (st.countTokens() == 0) { return false; } // Holder for Object at current depth along chain. Object current = object; try { // Loop through properties in chain. for (int i = 0; st.hasMoreTokens(); i++) { String currentPropertyName = st.nextToken(); if (i < st.countTokens()) { // This is a getter current = invokeProperty(current, currentPropertyName); } else { // Final property in chain, hence setter try { // Call setter Class cls = current.getClass(); PropertyDescriptor pd = new PropertyDescriptor(currentPropertyName, current.getClass()); pd.getWriteMethod().invoke(current, new Object[] {value}); return true; } catch (Exception e) { return false; } } } // Return holder Object return true; } catch (NullPointerException e) { // It is very likely that one of the properties returned null. If so, catch the exception and return null. return false; } } public Object getProperty(Object object, String property) { if ((property == null) || (object == null)) { return null; } // Split out property on dots ( "person.name.first" -> "person","name","first" -> getPerson().getName().getFirst() ) StringTokenizer st = new StringTokenizer(property, "."); if (st.countTokens() == 0) { return null; } // Holder for Object at current depth along chain. Object result = object; try { // Loop through properties in chain. while (st.hasMoreTokens()) { String currentPropertyName = st.nextToken(); // Assign to holder the next property in the chain. result = invokeProperty(result, currentPropertyName); } // Return holder Object return result; } catch (NullPointerException e) { // It is very likely that one of the properties returned null. If so, catch the exception and return null. return null; } } public void destroy() { } public void init() throws ProviderConfigurationException { } /** * Convert property name into getProperty name ( "something" -> "getSomething" ) */ private String createMethodName(String prefix, String propertyName) { return prefix + propertyName.toUpperCase().charAt(0) + propertyName.substring(1); } /** * Invoke the method/field getter on the Object. * It tries (in order) obj.getProperty(), obj.isProperty(), obj.property(), obj.property. */ private Object invokeProperty(Object obj, String property) { if ((property == null) || (property.length() == 0)) { return null; // just in case something silly happens. } Class cls = obj.getClass(); Object[] oParams = {}; Class[] cParams = {}; try { // First try object.getProperty() Method method = cls.getMethod(createMethodName(GET, property), cParams); return method.invoke(obj, oParams); } catch (Exception e1) { try { // First try object.isProperty() Method method = cls.getMethod(createMethodName(IS, property), cParams); return method.invoke(obj, oParams); } catch (Exception e2) { try { // Now try object.property() Method method = cls.getMethod(property, cParams); return method.invoke(obj, oParams); } catch (Exception e3) { try { // Now try object.property() Field field = cls.getField(property); return field.get(obj); } catch (Exception e4) { // oh well return null; } } } } }}?
oscore-2.2.5中的类，代码不难，且有注释，我就不多解析了。如有疑问，请提出来，我尽力解决。
try { // Call setter Class cls = current.getClass(); PropertyDescriptor pd = new PropertyDescriptor(currentPropertyName, current.getClass()); pd.getWriteMethod().invoke(current, new Object[] {value}); return true; } catch (Exception e) { return false; }