JSF动态生成组件
用过Servlet和JSP的开发者对动态生成组件应该是情有独钟了，可以根据数据的情况生成特定的组件，这样增大了Form的灵活性，那么JSF中如何生成动态的窗体呢，其实非常简单。主要逻辑就是通过FacesContext得到viewRoot对象，然后通过viewRoot对象的getChildren方法可以得到viewRoot下的所有第一级组件，然后分别对每个组件的getChildren方法进行递归调用，就可以得到整个组件树，当然可以对某个组件的getChildren得到的List使用add方法添加组件了，代码如下，页面有两个commandButton，其中一个可以添加一个TextBox控件，另外一个可以在console打印出当前的组件列表。
package net.moon;import java.util.List;import javax.faces.component.UIComponent;import javax.faces.component.UIViewRoot;import javax.faces.component.html.HtmlInputText;import javax.faces.context.FacesContext;
public class DymaComponent {
private UIViewRoot viewRoot; private static int inputIndex = 0;
private List<UIComponent> getComponentChildren(UIComponent component){
List<UIComponent> componentList = null; System.out.println(component.getId()); if(component.getChildCount() > 0){ for(UIComponent ui : component.getChildren()){ componentList = getComponentChildren(ui);
} } return componentList; } public String getComponentsList(){ viewRoot = FacesContext.getCurrentInstance().getViewRoot(); for(UIComponent component : viewRoot.getChildren()){ getComponentChildren(component); } return null; } public String addTextBox(){ viewRoot = FacesContext.getCurrentInstance().getViewRoot(); UIComponent form1 = viewRoot.getChildren().get(0); HtmlInputText input = new HtmlInputText(); input.setId("input" + (inputIndex++)); input.setValue("Input 1"); input.setRendered(true); form1.getChildren().add(input); return null; } 
}
<%@ page contentType="text/html; charset=UTF-8" %><%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %><%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %><html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> <title></title> </head> <body> <f:view> <h:form id="form1"> <h:commandButton id="commmand1" action="#{dymaComponent.getComponentsList}" value="Print ViewRoot"></h:commandButton> <h:commandButton action="#{dymaComponent.addTextBox}" value="Add TextBox"></h:commandButton> </h:form> </f:view> </body></html>
<?xml version="1.0" encoding="UTF-8"?><faces-config xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_1_2.xsd" version="1.2"> <managed-bean> <managed-bean-name> dymaComponent</managed-bean-name> <managed-bean-class> net.moon.DymaComponent</managed-bean-class> <managed-bean-scope> session</managed-bean-scope> </managed-bean></faces-config>
