My first reverse ajax application

StackOverflow https://stackoverflow.com/questions/10354503

質問

I want to learn about reverse ajax, I found a gadget called ICEPush and I thought it could be a good starting point. I am having trouble implementing a very simple application. I am following this tutorial, but instead of Tomcat, I am using Glassfish 3.1 and instead of Eclipse I am using NetBeans 7.1

I did exactly as it says in the tutorial, see my code. This is the page that will be the target of the Ajax push:

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core">
    <h:head>
        <title>Easy Ajax Push - Color</title>
    </h:head>

        <h:body>
            <h:dataTable value="#{messageBean.textList}" var="current">
                <h:column>
                    <h:outputText value="#{current.text}"
                                  style="color: #{current.color};"/>
                </h:column>
            </h:dataTable>

            <hr width="100%"/>

            <h:form>
                <h:panelGrid columns="4">
                    Choose a Color:
                    <h:commandButton value="Red"
                                     action="#{colorBean.chooseColor}"
                                     style="color: white; background-color: red;">
                        <f:setPropertyActionListener target="#{colorBean.color}" value="red"/>
                    </h:commandButton>
                    <h:commandButton value="Blue"
                                     action="#{colorBean.chooseColor}"
                                     style="color: white; background-color: blue;">
                        <f:setPropertyActionListener target="#{colorBean.color}" value="blue"/>
                    </h:commandButton>
                    <h:commandButton value="Green"
                                     action="#{colorBean.chooseColor}"
                                     style="color: white; background-color: green;">
                        <f:setPropertyActionListener target="#{colorBean.color}" value="green"/>
                    </h:commandButton>
                </h:panelGrid>
            </h:form>

        </h:body>

</html>

Here are the 2 managed beans that are needed: ColorBean.java

@ManagedBean(name="colorBean")
@ViewScoped
public class ColorBean implements  Serializable {

   private static final String PUSH_GROUP = "colorPage";

    @ManagedProperty(value="#{messageBean}")
    private MessageBean messageBean;
    private String color = "black";
    private String sessionId;

    public ColorBean() {            
                PushRenderer.addCurrentSession(PUSH_GROUP);
        FacesContext fcontext = FacesContext.getCurrentInstance();
        HttpSession session = (HttpSession)fcontext.getExternalContext().getSession(false);
        sessionId = session.getId();
    }

    public void setMessageBean(MessageBean messageBean) {
        this.messageBean = messageBean;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public String chooseColor() {
        messageBean.addToList(sessionId, color);
                PushRenderer.render(PUSH_GROUP);
        return null;
    }
}

MessageBean.java

@ManagedBean(name="messageBean")
@ApplicationScoped
public class MessageBean implements  Serializable {

    private static final int MAX_SIZE = 25;
    private List<TextModel> textList = new ArrayList<TextModel>(0);

    public MessageBean() {
    }

    public List<TextModel> getTextList() {
        return textList;
    }

    public void setTextList(List<TextModel> textList) {
        this.textList = textList;
    }

    public void addToList(String sessionId, String color) {
        textList.add(makeTextModel(sessionId, color));

        if (textList.size() > MAX_SIZE) {
            textList.clear();
        }
    }

    private TextModel makeTextModel(String sessionId, String color) {
        return new TextModel("User with session ID of " + sessionId + " selected color \"" + color + "\".",
                             color);
    }
}

Also there is a simple pojo to represent the text being presented. TextModel.java

public class TextModel implements Serializable {

    private String text;
    private String color;

    public TextModel() {
    }

    public TextModel(String text, String color) {
        this.text = text;
        this.color = color;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public String toString() {
        return text;
    }
}

I am using IceFaces version 3.0.1 and this is how my web.xml looks like:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 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-app_3_0.xsd">
    <context-param>
        <param-name>javax.faces.PROJECT_STAGE</param-name>
        <param-value>Development</param-value>
    </context-param>
    <context-param>
        <param-name>javax.faces.STATE_SAVING_METHOD</param-name>
        <param-value>server</param-value>
    </context-param>
    <context-param>
        <param-name>javax.faces.FACELETS_SKIP_COMMENTS</param-name>
        <param-value>true</param-value>
    </context-param>
    <context-param>
        <param-name>org.icefaces.mandatoryResourceConfiguration</param-name>
        <param-value/>
    </context-param>
    <context-param>
        <param-name>org.icefaces.ace.theme</param-name>
        <param-value>sam</param-value>
    </context-param>
    <context-param>
        <param-name>javax.faces.VALIDATE_EMPTY_FIELDS</param-name>
        <param-value>false</param-value>
    </context-param>
    <context-param>
        <param-name>com.icesoft.faces.gmapKey</param-name>
        <param-value>ABQIAAAADlu0ZiSTam64EKaCQr9eTRTOTuQNzJNXRlYRLknj4cQ89tFfpxTEqxQnVWL4k55OPICgF5_SOZE06A</param-value>
    </context-param>
    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet>
        <servlet-name>Resource Servlet</servlet-name>
        <servlet-class>com.icesoft.faces.webapp.CompatResourceServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>/faces/*</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>*.jsf</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>/icefaces/*</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>Resource Servlet</servlet-name>
        <url-pattern>/xmlhttp/*</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>faces/index.xhtml</welcome-file>
    </welcome-file-list>
</web-app>

This code gives me 3 problems:

1 - When i run the app and i click in some of the 3 buttons,get an exception that says that i cannot call one use one managed bean inside the other, because their scopes are not compatible:

WARNING: queued exception javax.faces.FacesException: Unable to create managed bean colorBean. The following problems were found: - The scope of the object referenced by expression #{messageBean}, request, is shorter than the referring managed beans (colorBean) scope of view

2 - In the console all the time i see a message that says:

WARNING: PWC4011: Unable to set request character encoding to UTF-8 from context /ReverseAjaxExample, because request parameters have already been read, or ServletRequest.getReader() has already been called

3 - If i change the @ApplicationScope to @ViewScope and the @ViewScope to @ApplicationScope in the managed beans, the first problem disappears and I can see how the application works, but the reverse ajax does not work, because other browsers do not display the changes. And also I always keep seeing the warning PWC4011 in the console

I never worked with reverse Ajax but I understand it from the theoretical point of view. I'll really appreciate it if you could give me a hand fixing this simple app.

役に立ちましたか？

解決

So many times it happens to me that i expend hours debugging and the reason of the bug was just the most simple thing.

Here i answer to my own question show how silly my mistake was:

Instead of using

javax.enterprise.context.ApplicationScoped

I should use

javax.faces.bean.ApplicationScoped

The reason is that i am not using Context and dependency injection, i am just using JSF managed beans.

Thanks to this i remembered it and i just refactored the imports, that's all Ctrl+Space doesn't like me :)

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