參數與<f:viewParam>和來自CDI的FacesConverter

Question

我不清楚爲什麼我得到這個特殊的例外，這是我認爲的一個紅鯡魚。根本問題可能與例外的最後一行有關：MessageConverter.getAsObject..0實際上應該是1501（消息ID）。那麼，爲什麼MessageConverter.getAsObject有錯誤的ID？

我認爲這可能與Detail構造函數有關，它可能將錯誤的參數傳遞給MessageConvert.getAsObject（），特別是UIComponent對象 - 可能需要實例化該引用。

相關EL：

 <h:outputLink id="link1" value="detail.xhtml"> 
      <f:param name="id" value="#{m.getMessageNumber()}" /> 
      <h:outputText value="#{m.getMessageNumber()}" /> 
     </h:outputLink> 

GlassFish中顯示：

INFO: MessageConverter.getAsObject..1501 
INFO: SingletonNNTP.forward..11 
WARNING: 1501 
java.lang.ArrayIndexOutOfBoundsException: 1501 
    at java.util.Arrays$ArrayList.get(Arrays.java:2866) 
    at net.bounceme.dur.nntp.SingletonNNTP.getMessage(SingletonNNTP.java:86) 
    at net.bounceme.dur.nntp.MessageConverter.getAsObject(MessageConverter.java:21) 
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue(HtmlBasicInputRenderer.java:171) 
    at javax.faces.component.UIViewParameter.getConvertedValue(UIViewParameter.java:394) 
    at javax.faces.component.UIInput.validate(UIInput.java:960) 
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1233) 
    at javax.faces.component.UIInput.processValidators(UIInput.java:698) 
    at javax.faces.component.UIViewParameter.processValidators(UIViewParameter.java:273) 
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) 
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) 
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1172) 
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76) 
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) 
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) 
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) 
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1542) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) 
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655) 
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161) 
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231) 
    at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317) 
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195) 
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:849) 
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:746) 
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1045) 
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:228) 
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137) 
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104) 
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90) 
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79) 
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54) 
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59) 
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71) 
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532) 
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513) 
    at java.lang.Thread.run(Thread.java:722) 

INFO: MessageConverter.getAsObject..0 
INFO: SingletonNNTP.forward..11 

的MessageConverter，我認爲這個類是精細迄今有云：

package net.bounceme.dur.nntp; 

import java.util.logging.Level; 
import java.util.logging.Logger; 
import javax.faces.component.UIComponent; 
import javax.faces.context.FacesContext; 
import javax.faces.convert.Converter; 
import javax.faces.convert.FacesConverter; 
import javax.mail.Message; 

@FacesConverter("messageConverter") 
public class MessageConverter implements Converter { 

    private static final Logger logger = Logger.getLogger(MessageConverter.class.getName()); 
    private static final Level level = Level.INFO; 
    private SingletonNNTP nntp = SingletonNNTP.INSTANCE; 

    @Override 
    public Object getAsObject(FacesContext context, UIComponent component, String value) { 
     logger.log(level, "MessageConverter.getAsObject..{0}", value); 
     Message message = nntp.getMessage(Integer.parseInt(value)); 
     return message; 
    } 

    @Override 
    public String getAsString(FacesContext context, UIComponent component, Object value) { 
     Message message = (Message) value; 
     return String.valueOf(message.getMessageNumber()); 
    } 
} 

這就是問題類，細節，與構造函數，特別是懷疑：

package net.bounceme.dur.nntp; 

import java.util.logging.Level; 
import java.util.logging.Logger; 
import javax.faces.component.UIComponent; 
import javax.faces.context.FacesContext; 
import javax.inject.Named; 
import javax.mail.Message; 

@Named 
public class Detail { 

    private static final Logger logger = Logger.getLogger(Detail.class.getName()); 
    private static final Level level = Level.INFO; 
    private int id = 0; 
    private Message message = null; 
    private SingletonNNTP nntp = SingletonNNTP.INSTANCE; 

    public Detail() { 
     MessageConverter mc = new MessageConverter(); 
     FacesContext fc = FacesContext.getCurrentInstance(); 
     String value = String.valueOf(id); 
     UIComponent ui = null; 
     Object obj = mc.getAsObject(fc, ui, value); 
     message = (Message) obj; 
    } 

    public int forward() { 
     logger.log(level, "Detail.forward..{0}", id); 
     id = id + 1; 
     logger.log(level, "..Detail.forward {0}", id); 
     return id; 
    } 

    public int back() { 
     logger.log(level, "Detail.back..{0}", id); 
     id = id - 1; 
     logger.log(level, "..Detail.back {0}", id); 
     return id; 
    } 

    public Message getMessage() { 
     return message; 
    } 

    public String getContent() throws Exception { 
     return message.getContent().toString(); 
    } 
} 

參考：

viewparam-vs-managedpropertyvalue-param-id這並不完全看起來就像我使用CDI，@Named，所以不能使用@ManagedProperty，這是「真正」的問題提出申請。我想我沒有看到CDI的好處，因爲@ManagedProperty看起來非常好。

ProcessingGETRequestParameters有，也許，關鍵段：

是的，這是一個@ManagedBean代替@FacesConverter！有多麼尷尬，但 無法在@FacesConverter中注入@EJB，以便按照 的順序執行數據庫交互作業。當您使用CDI @Inject注入屬性時，同樣的問題會出現，您需要使用@FacesConverter的@Named代替 。對於未來的JSF 2.2版本，Java EE/JSF/CDI傢伙正在爲此工作，另請參閱JSF規範問題763.如果您真的需要將其設置爲@FacesConverter（爲了利用 forClass屬性，例如），那麼您始終可以從JNDI手動抓取EJB。另見下一章。

這對我來說可能是因爲它與EJB有關而略有問題。但是，也許這就是我遇到的確切困難？

Answer 1

該轉換器應該用於<f:viewParam>。

<f:viewParam name="id" value="#{detail.message}" converter="messageConverter" /> 

這將基本轉換請求參數id反對Message，然後將其設置在後面#{detail.message}財產。你應該只在Detail類中爲它提供一個setter，我沒有在你的bean中看到任何一個。

您不應該在Detail類的構造函數中執行轉換作業。您應該只有Message財產，而不是id或nntp。刪除整個構造函數。

@Named 
public class Detail { 

    private Message message; 

    // Getters+setters+actions 
}