PrimeFaces Ajax下拉列表

PrimeFaces提供了一种基于过滤器创建动态下拉列表的简便方法。通过Ajax调用形成一个新的下拉列表。每个事件发生后, < p：ajax> 标记将调用Java方法。
在下面的示例中, 我们将创建两个下拉菜单。本示例包括以下文件。
JSF文件
// ajax-dropdown.xhtml

< ?xml version='1.0' encoding='UTF-8' ?> < !DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> < html xmlns="http://www.w3.org/1999/xhtml"xmlns:h="http://xmlns.jcp.org/jsf/html"xmlns:p="http://primefaces.org/ui"xmlns:f="http://xmlns.jcp.org/jsf/core"> < h:head> < title> Ajax Dropdown< /title> < /h:head> < h:body> < h:form> < p:growl id="msgs" showDetail="true" /> < p:panel header="Provide Your Address" style="margin-bottom:10px; "> < h:panelGrid columns="2" cellpadding="5"> < p:outputLabel for="country" value="http://www.srcmini.com/Country:" /> < p:selectOneMenu id="country" value="http://www.srcmini.com/#{dropdown.country}" style="width:150px"> < p:ajax listener="#{dropdown.onCountryChange}" update="city" /> < f:selectItem itemLabel="Select Country" itemValue="" noSelectionOption="true" /> < f:selectItems value="http://www.srcmini.com/#{dropdown.countries}" /> < /p:selectOneMenu> < p:outputLabel for="city" value="http://www.srcmini.com/City:" /> < p:selectOneMenu id="city" value="http://www.srcmini.com/#{dropdown.city}" style="width:150px"> < f:selectItem itemLabel="Select City" itemValue="" noSelectionOption="true" /> < f:selectItems value="http://www.srcmini.com/#{dropdown.cities}" /> < /p:selectOneMenu> < /h:panelGrid> < p:separator /> < p:commandButton value="http://www.srcmini.com/Submit" update="msgs" actionListener="#{dropdown.displayLocation}" icon="ui-icon-check" /> < /p:panel> < /h:form> < /h:body> < /html>

ManagedBean
// Dropdown.java

package com.srcmini; import java.io.Serializable; import java.util.HashMap; import java.util.Map; import javax.annotation.PostConstruct; import javax.faces.application.FacesMessage; import javax.faces.bean.ManagedBean; import javax.faces.bean.ViewScoped; import javax.faces.context.FacesContext; @ManagedBean@ViewScopedpublic class Dropdown implements Serializable {private final Map< String, Map< String, String> > data = http://www.srcmini.com/new HashMap< > (); private String country; private String city; private Map< String, String> countries; private Map< String, String> cities; @PostConstructpublic void init() {countries= new HashMap< > (); countries.put("USA", "USA"); countries.put("India", "India"); countries.put("Russia", "Russia"); Map< String, String> map = new HashMap< > (); map.put("New York", "New York"); map.put("San Francisco", "San Francisco"); map.put("Denver", "Denver"); data.put("USA", map); map = new HashMap< > (); map.put("New Delhi", "New Delhi"); map.put("Bombay", "Bombay"); map.put("Calcutta", "Calcutta"); data.put("India", map); map = new HashMap< > (); map.put("Moscow", "Moscow"); map.put("Saint Petersburg", "Saint Petersburg"); map.put("Samara", "Samara"); data.put("Russia", map); }public Map< String, Map< String, String> > getData() {return data; }public String getCountry() {return country; }public void setCountry(String country) {this.country = country; }public String getCity() {return city; }public void setCity(String city) {this.city = city; }public Map< String, String> getCountries() {return countries; }public Map< String, String> getCities() {return cities; }public void onCountryChange() {if(country !=null & & !country.equals(""))cities = data.get(country); elsecities = new HashMap< > (); }public void displayLocation() {FacesMessage msg; if(city != null & & country != null)msg = new FacesMessage("Selected", city + " of " + country); elsemsg = new FacesMessage(FacesMessage.SEVERITY_ERROR, "Invalid", "City is not selected."); FacesContext.getCurrentInstance().addMessage(null, msg); }}package com.srcmini; import java.io.Serializable; import java.util.HashMap; import java.util.Map; import javax.annotation.PostConstruct; import javax.faces.application.FacesMessage; import javax.faces.bean.ManagedBean; import javax.faces.bean.ViewScoped; import javax.faces.context.FacesContext; @ManagedBean@ViewScopedpublic class Dropdown implements Serializable {private final Map< String, Map< String, String> > data = http://www.srcmini.com/new HashMap< > (); private String country; private String city; private Map< String, String> countries; private Map< String, String> cities; @PostConstructpublic void init() {countries= new HashMap< > (); countries.put("USA", "USA"); countries.put("India", "India"); countries.put("Russia", "Russia"); Map< String, String> map = new HashMap< > (); map.put("New York", "New York"); map.put("San Francisco", "San Francisco"); map.put("Denver", "Denver"); data.put("USA", map); map = new HashMap< > (); map.put("New Delhi", "New Delhi"); map.put("Bombay", "Bombay"); map.put("Calcutta", "Calcutta"); data.put("India", map); map = new HashMap< > (); map.put("Moscow", "Moscow"); map.put("Saint Petersburg", "Saint Petersburg"); map.put("Samara", "Samara"); data.put("Russia", map); }public Map< String, Map< String, String> > getData() {return data; }public String getCountry() {return country; }public void setCountry(String country) {this.country = country; }public String getCity() {return city; }public void setCity(String city) {this.city = city; }public Map< String, String> getCountries() {return countries; }public Map< String, String> getCities() {return cities; }public void onCountryChange() {if(country !=null & & !country.equals(""))cities = data.get(country); elsecities = new HashMap< > (); }public void displayLocation() {FacesMessage msg; if(city != null & & country != null)msg = new FacesMessage("Selected", city + " of " + country); elsemsg = new FacesMessage(FacesMessage.SEVERITY_ERROR, "Invalid", "City is not selected."); FacesContext.getCurrentInstance().addMessage(null, msg); }}

执行后, 将产生以下输出。
输出