2.AJAX处理服务器组件
这个组件接受来自浏览器的AJAX请求，返回响应。AJAX服务器组件可以实现成
a.完全独立的HTTP服务器对象，例如通过servlet.
b.集成到JSF应用程序的AJAX服务对象。例如组件的decode()方法货PhaseListener充当AJAX服务器组件。
对于使用decode()方法充当服务器组件还要再讨论下。
虽然对于decode()的拦截方法有如下定义：“对于请求的一个非常重要的要求是：表单名称也必须做为参数传递给JSF应用程序。如果没有传递这个值,JSF应用程序会吧请求解释为 none-post-back请求，所以不会进入decode()方法。所以生成的response是非AJAX的完整HTML页面。可以用一下JavaScript代码把formName 和 ajaxreq参数组合在一起。
var formdata = "formName=" + window.document.forms[0].id + "&ajaxreq=true";”
但本人查阅了部分资料发现decode()方法现在已经不能拦截AJAX post-back请求了。但即使把表单名称(window.docuent.forms[0].id)传递进去也不会被JSF应用程序当作post-back请求而进入decode()方法。官方推荐方法是使用PhaseListener充当AJAX服务器组件。
接下来给出PhaseListener的实现DataProviderPhListener.java 。在这段代码离不仅拦截了AJAX post-back请求而且还渲染了上段gridajax.js代码到页面内。
请注意
public PhaseId getPhaseId() {
return PhaseId.ANY_PHASE;
}由于每次阶段变化都执行它，所以返回ANY_PHASE。在beforePhase中只接受生命周期的第六个阶段所以使用PhaseId.RENDER_RESPONSE，而在在afterPhase中只接受生命周期的第一个阶段所以使用PhaseId.RESTORE_VIEWDataProviderPhListener.java
package phaselistener;
import java.io.BufferedReader;
import java.util.Map;
import javax.faces.context.FacesContext;
import javax.faces.event.PhaseEvent;
import javax.faces.event.PhaseId;
import javax.faces.event.PhaseListener;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.net.URLConnection;
import javax.faces.FactoryFinder;
import javax.faces.context.ResponseWriter;
import javax.faces.el.EvaluationException;
import javax.faces.render.RenderKit;
import javax.faces.render.RenderKitFactory;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import util.JSONGenerator;
/**
*
* @author love
*/
public class DataProviderPhListener implements PhaseListener {
public static final String RENDER_SCRIPT_VIEW_ID = "SpellCheckTextArea.ajaxScript";
private static final String SCRIPT_RESOURCE_NAME = "/com/jsfcompref/components/component/gridajax.js";
public PhaseId getPhaseId() {
return PhaseId.ANY_PHASE;
}
/**
* <p>Go through each component in the AJAX_VALIDATOR_COMPONENTS
* list in request scope.
*/
public void afterPhase(PhaseEvent event) {
// If this is restoreView phase and the viewId is the script view id
if(event.getPhaseId() == PhaseId.RESTORE_VIEW){
if (-1 != event.getFacesContext().getViewRoot().getViewId().indexOf(RENDER_SCRIPT_VIEW_ID) &&
PhaseId.RESTORE_VIEW == event.getPhaseId()) {
// render the script
writeScript(event);
event.getFacesContext().responseComplete();
}
}
}
public void beforePhase(PhaseEvent event) {
if (event.getPhaseId() == PhaseId.RENDER_RESPONSE) {
FacesContext context = event.getFacesContext();
Map requestMap = context.getExternalContext().getRequestParameterMap();
if (requestMap.containsKey("ajaxreq")) {
HttpServletResponse response =
(HttpServletResponse) context.getExternalContext().getResponse();
HttpServletRequest request =
(HttpServletRequest) context.getExternalContext().getRequest();
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
try {
ResponseWriter writer = FacesContext.getCurrentInstance().getResponseWriter();
if (null == writer) {
RenderKitFactory rkf = (RenderKitFactory) FactoryFinder.getFactory(FactoryFinder.RENDER_KIT_FACTORY);
RenderKit renderKit = rkf.getRenderKit(context, context.getViewRoot().getRenderKitId());
writer = renderKit.createResponseWriter(response.getWriter(), "text/html", request.getCharacterEncoding());
context.setResponseWriter(writer);
}
JSONGenerator jsonGen = new JSONGenerator(request.getParameter("input"), context);
String jsonOut = jsonGen.getJsonResponse();
writer.write(jsonOut);
context.responseComplete();
// return;
} catch (EvaluationException ee) {
ee.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}
}
private void writeScript(PhaseEvent event) {
URL url = getClass().getResource(SCRIPT_RESOURCE_NAME);
URLConnection conn = null;
InputStream stream = null;
BufferedReader bufReader = null;
HttpServletResponse response = (HttpServletResponse) event.getFacesContext().getExternalContext().getResponse();
OutputStreamWriter outWriter = null;
String curLine = null;
response.setCharacterEncoding("GBK");
try {
outWriter = new OutputStreamWriter(response.getOutputStream(),
response.getCharacterEncoding());
conn = url.openConnection();
conn.setUseCaches(false);
stream = conn.getInputStream();
bufReader = new BufferedReader(new InputStreamReader(stream));
response.setContentType("text/javascript;charset=UTF-8");
response.setStatus(200);
while (null != (curLine = bufReader.readLine())) {
outWriter.write(curLine + "\n");
}
outWriter.flush();
outWriter.close();
} catch (Exception e) {
String message = null;
message = "Can't load script file:" +
url.toExternalForm();
try {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, message);
} catch (IOException f) {
f.printStackTrace();
}
}
}
}
这里使用了一个助手类JSONGenerator用于将查询数据库得到的结果转化成dojo.Grid可以接受的JSON格式这里的数据库查询操作使用了NetBean提供的DataProvider。感觉很像.NET的数据绑定技术。
JSONGenerator.java
package util;
import com.sun.data.provider.impl.CachedRowSetDataProvider;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;
import javax.faces.application.FacesMessage;
import javax.faces.context.FacesContext;
import javax.faces.el.ValueBinding;
import javax.sql.rowset.CachedRowSet;
import org.json.JSONArray;
import org.json.JSONObject;
import webapplication3.SessionBean1;
/**
*
* @author love
*/
public class JSONGenerator {
private String jsonResponse;
private CachedRowSetDataProvider personDataProvider = new CachedRowSetDataProvider();
public CachedRowSetDataProvider getPersonDataProvider() {
return personDataProvider;
}
public void setPersonDataProvider(CachedRowSetDataProvider crsdp) {
this.personDataProvider = crsdp;
}
public JSONGenerator(String input,FacesContext context){
ValueBinding vb = context.getApplication().createValueBinding("#{SessionBean1.personRowSet}");
personDataProvider.setCachedRowSet((CachedRowSet) vb.getValue(context));
// SessionBean1 sessionb = (SessionBean1)context.getApplication().getVariableResolver().resolveVariable(context, "SessionBean1");
SessionBean1 sessiona = (SessionBean1)context.getApplication().getELResolver().getValue(context.getELContext(), null, "SessionBean1");
// SessionBean1 sessionb = (SessionBean1) JSFUtil.getManagedObject("#{SessionBean1}",SessionBean1.class);
try {
sessiona.getPersonRowSet().setObject(1, input.toUpperCase()+"%");
personDataProvider.refresh();
CachedRowSet cache = personDataProvider.getCachedRowSet();
cache.execute();
ResultSet rs = cache.getOriginal();
JSONArray list = new JSONArray();
try {
while (rs.next()) {
JSONObject jsobj = new JSONObject();
String id = rs.getString("PERSONID");
String name = rs.getString("NAME");
String job = rs.getString("JOBTITLE");
String fre = rs.getString("FREQUENTFLYER");
Date date = rs.getDate("LASTUPDATED");
jsobj.put("LASTUPDATED", date==null?"":date);
jsobj.put("FREQUENTFLYER", !fre.isEmpty()?fre:"");
jsobj.put("JOBTITLE", !job.isEmpty()?job:"");
jsobj.put("NAME", !name.isEmpty()?name:"");
jsobj.put("PERSONID", !id.isEmpty()?id:"");
list.put(jsobj);
}
String jsonText = list.toString();
jsonText = jsonText.replace('\"', '\'');
jsonResponse = "{" + String.format("identifier: 'PERSONID', label: 'NAME', items: %1$s", jsonText) + "}";
} catch (SQLException ex) {
context.addMessage(null,
new FacesMessage(FacesMessage.SEVERITY_ERROR, "Cannot switch to person " + personDataProvider.getValue("PERSON.PERSONID"), null));
}
}catch (Exception e) {
e.printStackTrace();
}
}
/**
* @return the jsonResponse
*/
public String getJsonResponse() {
return jsonResponse;
}
/**
* @param jsonResponse the jsonResponse to set
*/
public void setJsonResponse(String jsonResponse) {
this.jsonResponse = jsonResponse;
}
}