JSF中引入jsf.js文件之后，可以拦截jsf.ajax.request请求。一直希望有一种方法可以像jquery的ajax一样，能在js中异步取得服务器端发送的数据。无奈标准JSF并没有提供这样的方法。在一些JSF框架里面提供了这样的方法，比如primefaces的onComplete方法就是返回数据到一个js方法中的。JSF能在bean里面更新视图（非ajax更新），其中的PartialViewContext类就可以做到局部更新UI，在bean里获取到这个UI就可以了。于是在网上翻看了很多开源的JSF框架，无意中发现omnifaces这个开源框架。官网:http://omnifaces.org/。
当然，一个框架的东西会有很多，以个人之力要全部参透会有一些难度。开源框架更是集思广益，不过我所需要的只是其中的一部分而已，即在js中取得bean返回的数据。
根据omnifaces的showcase http://showcase.omnifaces.org/ 看到其中的一个Ajax工具类根据PartialViewContext类做到了js取得返回数据，不论字符串或者对象数据都可以发送，非常方便。于是根据提供的源码，顺藤摸瓜，copy了必须支持的类，整理出来了一个仅Ajax发送数据的jar。
omnifaces做的步骤大概是先重写了PartialViewContextFactory这个类，然后在配置文件中配置该重写的类。
1 /**
2 * This partial view context factory takes care that the {@link OmniPartialViewContext} is properly initialized.
3 *
4 */
5 public class CustomPartialViewContextFactory extends PartialViewContextFactory {
6
7 // Variables ------------------------------------------------------------------------------------------------------
8
9 private PartialViewContextFactory wrapped;
10
11 // Constructors ---------------------------------------------------------------------------------------------------
12
13 /**
14 * Construct a new OmniFaces partial view context factory around the given wrapped factory.
15 * @param wrapped The wrapped factory.
16 */
17 public CustomPartialViewContextFactory(PartialViewContextFactory wrapped) {
18 this.wrapped = wrapped;
19 }
20
21 // Actions --------------------------------------------------------------------------------------------------------
22
23 /**
24 * Returns a new instance of {@link OmniPartialViewContext} which wraps the original partial view context.
25 */
26 @Override
27 public PartialViewContext getPartialViewContext(FacesContext context) {
28 return new CustomPartialViewContext(wrapped.getPartialViewContext(context));
29 }
30
31 /**
32 * Returns the wrapped factory.
33 */
34 @Override
35 public PartialViewContextFactory getWrapped() {
36 return wrapped;
37 }
38
39 }
该类重写还需要一个PartialViewContext ，此处没有直接继承PartialViewContext ，而是继承了PartialViewContext 的子类PartialViewContextWrapper，并重写了里面的方法：
1 /**
2 * <p>
3 * This OmniFaces partial view context extends and improves the standard partial view context as follows:
4 * <ul>
5 * <li>Support for executing callback scripts by {@link PartialResponseWriter#startEval()}.</li>
6 * <li>Support for adding arguments to an ajax response.</li>
7 * <li>Any XML tags which Mojarra and MyFaces has left open after an exception in rendering of an already committed
8 * ajax response, will now be properly closed. This prevents errors about malformed XML.</li>
9 * <li>Fixes the no-feedback problem when a {@link ViewExpiredException} occurs during an ajax request on a page which
10 * is restricted by <code>web.xml</code> <code><security-constraint></code>. The enduser will now properly be
11 * redirected to the login page instead of retrieving an ajax response with only a changed view state (and effectively
12 * thus no visual feedback at all).</li>
13 * </ul>
14 * You can use the {@link Ajax} utility class to easily add callback scripts and arguments.
15 * <p>
16 * This partial view context is already registered by OmniFaces‘ own <code>faces-config.xml</code> and thus gets
17 * auto-initialized when the OmniFaces JAR is bundled in a web application, so end-users do not need to register this
18 * partial view context explicitly themselves.
19 *
20 * @author Bauke Scholtz
21 * @since 1.2
22 * @see OmniPartialViewContextFactory
23 */
24 public class CustomPartialViewContext extends PartialViewContextWrapper {
25
26 // Constants ------------------------------------------------------------------------------------------------------
27
28 private static final String AJAX_DATA = "var Faces=Faces||{};Faces.Ajax={data:%s};";
29 private static final String ERROR_NO_OMNI_PVC = "There is no current CustomPartialViewContext instance.";
30
31 // Variables ------------------------------------------------------------------------------------------------------
32
33 private PartialViewContext wrapped;
34 private Map<String, Object> arguments;
35 private List<String> callbackScripts;
36 private CustomPartialResponseWriter writer;
37
38 // Constructors ---------------------------------------------------------------------------------------------------
39
40 /**
41 * Construct a new OmniFaces partial view context around the given wrapped partial view context.
42 * @param wrapped The wrapped partial view context.
43 */
44 public CustomPartialViewContext(PartialViewContext wrapped) {
45 this.wrapped = wrapped;
46 setCurrentInstance(this);
47 }
48
49 // Actions --------------------------------------------------------------------------------------------------------
50
51 @Override
52 public PartialResponseWriter getPartialResponseWriter() {
53 if (writer == null) {
54 writer = new CustomPartialResponseWriter(this, super.getPartialResponseWriter());
55 }
56
57 return writer;
58 }
59
60 @Override // Necessary because this is missing in PartialViewContextWrapper (will be fixed in JSF 2.2).
61 public void setPartialRequest(boolean partialRequest) {
62 getWrapped().setPartialRequest(partialRequest);
63 }
64
65 @Override
66 public PartialViewContext getWrapped() {
67 return wrapped;
68 }
69
70 /**
71 * Add an argument to the partial response. This is as JSON object available by <code>OmniFaces.Ajax.data</code>.
72 * For supported argument value types, read {@link Json#encode(Object)}. If a given argument type is not supported,
73 * then an {@link IllegalArgumentException} will be thrown during end of render response.
74 * @param name The argument name.
75 * @param value The argument value.
76 */
77 public void addArgument(String name, Object value) {
78 if (arguments == null) {
79 arguments = new HashMap<>();
80 }
81
82 arguments.put(name, value);
83 }
84
85 /**
86 * Add a callback script to the partial response. This script will be executed once the partial response is
87 * successfully retrieved at the client side.
88 * @param callbackScript The callback script to be added to the partial response.
89 */
90 public void addCallbackScript(String callbackScript) {
91 if (callbackScripts == null) {
92 callbackScripts = new ArrayList<>();
93 }
94
95 callbackScripts.add(callbackScript);
96 }
97
98 /**
99 * Reset the partial response. This clears any JavaScript arguments and callbacks set any data written to the
100 * {@link PartialResponseWriter}.
101 * @see FullAjaxExceptionHandler
102 */
103 public void resetPartialResponse() {
104 if (writer != null) {
105 writer.reset();
106 }
107
108 arguments = null;
109 callbackScripts = null;
110 }
111
112 /**
113 * Close the partial response. If the writer is still in update phase, then end the update and the document. This
114 * fixes the Mojarra problem of incomplete ajax responses caused by exceptions during ajax render response.
115 * @see FullAjaxExceptionHandler
116 */
117 public void closePartialResponse() {
118 if (writer != null && writer.updating) {
119 try {
120 writer.endUpdate();
121 writer.endDocument();
122 }
123 catch (IOException e) {
124 throw new FacesException(e);
125 }
126 }
127 }
128
129 // Static ---------------------------------------------------------------------------------------------------------
130
131 /**
132 * Returns the current instance of the OmniFaces partial view context.
133 * @return The current instance of the OmniFaces partial view context.
134 * @throws IllegalStateException When there is no current instance of the OmniFaces partial view context. That can
135 * happen when the {@link OmniPartialViewContextFactory} is not properly registered, or when there‘s another
136 * {@link PartialViewContext} implementation which doesn‘t properly delegate through the wrapped instance.
137 */
138 public static CustomPartialViewContext getCurrentInstance() {
139 return getCurrentInstance(getContext());
140 }
141
142 /**
143 * Returns the current instance of the OmniFaces partial view context from the given faces context.
144 * @param context The faces context to obtain the current instance of the OmniFaces partial view context from.
145 * @return The current instance of the OmniFaces partial view context from the given faces context.
146 * @throws IllegalStateException When there is no current instance of the OmniFaces partial view context. That can
147 * happen when the {@link OmniPartialViewContextFactory} is not properly registered, or when there‘s another
148 * {@link PartialViewContext} implementation which doesn‘t properly delegate through the wrapped instance.
149 */
150 public static CustomPartialViewContext getCurrentInstance(FacesContext context) {
151 CustomPartialViewContext instance = getContextAttribute(context, CustomPartialViewContext.class.getName());
152
153 if (instance != null) {
154 return instance;
155 }
156
157 // Not found. Well, maybe the context attribute map was cleared for some reason. Get it once again.
158 instance = unwrap(context.getPartialViewContext());
159
160 if (instance != null) {
161 setCurrentInstance(instance);
162 return instance;
163 }
164
165 // Still not found. Well, maybe RichFaces is installed which doesn‘t use PartialViewContextWrapper.
166 if (Hacks.isRichFacesInstalled()) {
167 PartialViewContext pvc = Hacks.getRichFacesWrappedPartialViewContext();
168
169 if (pvc != null) {
170 instance = unwrap(pvc);
171
172 if (instance != null) {
173 setCurrentInstance(instance);
174 return instance;
175 }
176 }
177 }
178
179 // Still not found. Well, it‘s end of story.
180 throw new IllegalStateException(ERROR_NO_OMNI_PVC);
181 }
182
183 private static void setCurrentInstance(CustomPartialViewContext instance) {
184 setContextAttribute(CustomPartialViewContext.class.getName(), instance);
185 }
186
187 private static CustomPartialViewContext unwrap(PartialViewContext context) {
188 PartialViewContext unwrappedContext = context;
189
190 while (!(unwrappedContext instanceof CustomPartialViewContext) && unwrappedContext instanceof PartialViewContextWrapper) {
191 unwrappedContext = ((PartialViewContextWrapper) unwrappedContext).getWrapped();
192 }
193
194 if (unwrappedContext instanceof CustomPartialViewContext) {
195 return (CustomPartialViewContext) unwrappedContext;
196 }
197 else {
198 return null;
199 }
200 }
201
202 // Nested classes -------------------------------------------------------------------------------------------------
203
204 /**
205 * This OmniFaces partial response writer adds support for passing arguments to JavaScript context, executing
206 * oncomplete callback scripts, resetting the ajax response (specifically for {@link FullAjaxExceptionHandler}) and
207 * fixing incomlete XML response in case of exceptions.
208 * @author Bauke Scholtz
209 */
210 private static class CustomPartialResponseWriter extends PartialResponseWriter {
211
212 // Variables --------------------------------------------------------------------------------------------------
213
214 private CustomPartialViewContext context;
215 private PartialResponseWriter wrapped;
216 private boolean updating;
217
218 // Constructors -----------------------------------------------------------------------------------------------
219
220 public CustomPartialResponseWriter(CustomPartialViewContext context, PartialResponseWriter wrapped) {
221 super(wrapped);
222 this.wrapped = wrapped; // We can‘t rely on getWrapped() due to MyFaces broken PartialResponseWriter.
223 this.context = context;
224 }
225
226 // Overridden actions -----------------------------------------------------------------------------------------
227
228 /**
229 * An override which checks if the web.xml security constraint has been triggered during this ajax request
230 * (which can happen when the session has been timed out) and if so, then perform a redirect to the originally
231 * requested page. Otherwise the enduser ends up with an ajax response containing only the new view state
232 * without any form of visual feedback.
233 */
234 @Override
235 public void startDocument() throws IOException {
236 wrapped.startDocument();
237 String loginURL = WebXml.INSTANCE.getFormLoginPage();
238
239 if (loginURL != null) {
240 FacesContext facesContext = FacesContext.getCurrentInstance();
241 String loginViewId = normalizeViewId(facesContext, loginURL);
242
243 if (loginViewId.equals(getViewId(facesContext))) {
244 String originalURL = getRequestAttribute(facesContext, "javax.servlet.forward.request_uri");
245
246 if (originalURL != null) {
247 redirect(originalURL);
248 }
249 }
250 }
251 }
252
253 /**
254 * An override which remembers if we‘re updating or not.
255 * @see #endDocument()
256 * @see #reset()
257 */
258 @Override
259 public void startUpdate(String targetId) throws IOException {
260 updating = true;
261 wrapped.startUpdate(targetId);
262 }
263
264 /**
265 * An override which remembers if we‘re updating or not.
266 * @see #endDocument()
267 * @see #reset()
268 */
269 @Override
270 public void endUpdate() throws IOException {
271 updating = false;
272 wrapped.endUpdate();
273 }
274
275 /**
276 * An override which writes all {@link OmniPartialViewContext#arguments} as JSON to the extension and all
277 * {@link OmniPartialViewContext#callbackScripts} to the eval. It also checks if we‘re still updating, which
278 * may occur when MyFaces is used and an exception was thrown during rendering the partial response, and then
279 * gently closes the partial response which MyFaces has left open.
280 */
281 @Override
282 public void endDocument() throws IOException {
283 if (updating) {
284 // If endDocument() method is entered with updating=true, then it means that MyFaces is used and that
285 // an exception was been thrown during ajax render response. The following calls will gently close the
286 // partial response which MyFaces has left open.
287 // Mojarra never enters endDocument() method with updating=true, this is handled in reset() method.
288 endCDATA();
289 endUpdate();
290 }
291 else {
292 if (context.arguments != null) {
293 startEval();
294 write(String.format(AJAX_DATA, Json.encode(context.arguments)));
295 endEval();
296 }
297
298 if (context.callbackScripts != null) {
299 for (String callbackScript : context.callbackScripts) {
300 startEval();
301 write(callbackScript);
302 endEval();
303 }
304 }
305 }
306
307 wrapped.endDocument();
308 }
309
310 // Custom actions ---------------------------------------------------------------------------------------------
311
312 /**
313 * Reset the partial response writer. It checks if we‘re still updating, which may occur when Mojarra is used
314 * and an exception was thrown during rendering the partial response, and then gently closes the partial
315 * response which Mojarra has left open. This would clear the internal state of the wrapped partial response
316 * writer and thus make it ready for reuse without risking malformed XML.
317 */
318 public void reset() {
319 try {
320 if (updating) {
321 // If reset() method is entered with updating=true, then it means that Mojarra is used and that
322 // an exception was been thrown during ajax render response. The following calls will gently close
323 // the partial response which Mojarra has left open.
324 // MyFaces never enters reset() method with updating=true, this is handled in endDocument() method.
325 endCDATA();
326 endUpdate();
327 wrapped.endDocument();
328 }
329 }
330 catch (IOException e) {
331 throw new FacesException(e);
332 }
333 finally {
334 responseReset();
335 }
336 }
337
338 // Delegate actions -------------------------------------------------------------------------------------------
339 // Due to MyFaces broken PartialResponseWriter, which doesn‘t delegate to getWrapped() method, but instead to
340 // the local variable wrapped, we can‘t use getWrapped() in our own PartialResponseWriter implementations.
341
342 @Override
343 public void startError(String errorName) throws IOException {
344 wrapped.startError(errorName);
345 }
346
347 @Override
348 public void startEval() throws IOException {
349 wrapped.startEval();
350 }
351
352 @Override
353 public void startExtension(Map<String, String> attributes) throws IOException {
354 wrapped.startExtension(attributes);
355 }
356
357 @Override
358 public void startInsertAfter(String targetId) throws IOException {
359 wrapped.startInsertAfter(targetId);
360 }
361
362 @Override
363 public void startInsertBefore(String targetId) throws IOException {
364 wrapped.startInsertBefore(targetId);
365 }
366
367 @Override
368 public void endError() throws IOException {
369 wrapped.endError();
370 }
371
372 @Override
373 public void endEval() throws IOException {
374 wrapped.endEval();
375 }
376
377 @Override
378 public void endExtension() throws IOException {
379 wrapped.endExtension();
380 }
381
382 @Override
383 public void endInsert() throws IOException {
384 wrapped.endInsert();
385 }
386
387 @Override
388 public void delete(String targetId) throws IOException {
389 wrapped.delete(targetId);
390 }
391
392 @Override
393 public void redirect(String url) throws IOException {
394 wrapped.redirect(url);
395 }
396
397 @Override
398 public void updateAttributes(String targetId, Map<String, String> attributes) throws IOException {
399 wrapped.updateAttributes(targetId, attributes);
400 }
401
402 }
403 }
可以看到其中定义了两个常量，一个警告说明，一个名为AJAX_DATA，里面写的是一段js的字符串。这个常量用在了 被重写的endDocument()方法里。这个方法主要做了两件事，第一是写入要传递的数据，并且以json格式打包，第二件事是包含了一个js方法。那么可以这样认为：该方法的作用是用一个js方法取得发送的数据。
首先我们必须清楚，JSF使用f:ajax更新客户端的底层操作是怎样的。JSF更新数据是向页面发送了xml数据的，可以在firefox的 firebug下面的网络-XML面板下看到发送的xml数据，类似于以下的数据：
1 <partial-response id="j_id1"> 2 <changes> 3 <update id="j_id1:javax.faces.ViewState:0">-4426271603414575392:-5845678956333562288</update> 4 </changes> 5 </partial-response>
里面包含了需要更新的组件和组件状态。
我把omnifaces的Ajax代码整理出来以后，根据官方例子的用法，写了一个小demo测试，其中页面form表单代码如下：
1 <h:form prependId="false">
2 <h:outputLabel value="#{test2.radom}" id="outLabel"/>
3 <h:commandButton action="#{test2.callback}" value="请求服务端js">
4 <f:ajax/>
5 </h:commandButton>
6 <h:commandButton value="获取服务端数据到js">
7 <f:ajax listener="#{test2.argument}"/>
8 </h:commandButton>
9
10 <h:commandButton value="showUser">
11 <f:ajax listener="#{test2.parseUser}"/>
12 </h:commandButton>
13 </h:form>
测试bean代码如下：
1 @ManagedBean(name="test2")
2 @ViewScoped
3 public class Test2 implements Serializable {
4
5 private static final long serialVersionUID = 8686669721840131192L;
6
7 public void callback() {
8 Ajax.oncomplete("alert(‘Hi, I am the oncomplete callback script!‘)");
9 }
10
11 public void argument() {
12 Ajax.data("foo", "bar");
13 Ajax.data("first", "one", "second", "two");
14 Map<String, Object> data = new HashMap<>();
15 data.put("bool", true);
16 data.put("number", 1.2F);
17 data.put("date", new Date());
18 data.put("array", new Integer[] { 1, 2, 3, 4, 5 });
19 data.put("list", Arrays.asList("one", "two", "three"));
20 Ajax.data(data);
21 Ajax.oncomplete("showData()");
22 }
23
24 public void parseUser(){
25 Ajax.data("user", new User(1, "bigbang"));
26 Ajax.oncomplete("showUser()");
27 }
28
29 }
其中提供了三个页面响应的方法。当点击第一个button时，页面会弹出一个alert提示框。此时查看firefox下面的数据如下：
1 <partial-response id="j_id1"> 2 <changes> 3 <update id="j_id1:javax.faces.ViewState:0">-4426271603414575392:-5845678956333562288</update> 4 <eval>alert(‘Hi, I am the oncomplete callback script!‘)</eval> 5 </changes> 6 </partial-response>
点击“获取数据到js”按钮，查看xml数据：
1 <partial-response id="j_id1">
2 <changes>
3 <update id="j_id1:javax.faces.ViewState:0">-3364647386979820288:-1391656100755852530</update>
4 <eval>var Faces=Faces||{};Faces.Ajax={data:{"second":"two","number":1.2,"list":["one","two","three"],"foo":"bar","bool":true,"date":"Fri, 17 Jul 2015 09:17:50 GMT","first":"one","array":[1,2,3,4,5]}};</eval>
5 <eval>showData()</eval>
6 </changes>
7 </partial-response>
点击“showuser”按钮，查看xml数据：
1 <partial-response id="j_id1">
2 <changes>
3 <update id="j_id1:javax.faces.ViewState:0">-3364647386979820288:-1391656100755852530</update>
4 <eval>var Faces=Faces||{};Faces.Ajax={data:{"user":{"id":1,"name":"bigbang"}}};</eval>
5 <eval>showUser()</eval>
6 </changes>
7 </partial-response>
可以看出刚才的那个endDocumnt方法和AJAX_DATA常量的用意了，实际是构造了一个js对象，然后传入一个js方法到客户端，客户端会自动调用这个js方法，根据对象取得json数据。那么客户端的js只需要这样写就可以了：
1 <script>
2 function showData() {
3 var data = Faces.Ajax.data;
4 $.each(data, function(key, value) {
5 console.log(key+"---"+JSON.stringify(value));
6 });
7 }
8
9 function showUser(){
10 var data = Faces.Ajax.data;
11 $.each(data, function(key,value){
12 var user = JSON.stringify(value);
13 var u = $.parseJSON(user);
14 console.log("userName----"+u.name);
15 }
16 </script>
控制台显示数据如下：
OK，大功告成了！其中的细节不用细究，无非就是掺杂了各种数据转换为json格式、数据的包装和写入。最后说明一点，omnifaces需要CDI的支持，必须导入CDI的jar包。
时间： 2024-12-16 06:55:50