动态Jfreechart

Question

我有一个问题，使primefaces动态图像工作。我想我所做的与primefaces showcase上的示例完全一样，但是图像并没有加载到页面上。我的托管bean如下所示。

@ManagedBean(name = "statisticsBean")
@NoneScoped
public class StatisticsBean {

    private WMCUser user;
    private BasicGroup group;
    private List<GameProgressStatistics> lineChartStats;
    private List<UserStatistics> userStatistics;
    private static final Logger logger = Logger.getLogger(StatisticsBean.class.getName());

public StatisticsBean() {
        ...
        createUserStatistics();
}

private void createUserStatistics() {
    List<WMCUser> users = GroupHelper.getNonDeletedMembers(group);
    for (WMCUser wmcUser : users) {
        userStatistics.add(new UserStatistics(
                wmcUser.getStatUser().getMakeCount(),
                wmcUser.getStatUser().getGamesPlayed(),
                wmcUser.getFirstName(),
                wmcUser.getLastName()));
    }
}

      public class UserStatistics {

        private int makeCount;
        private int gameCount;
        private String firstName;
        private String lastName;
        private StreamedContent thermoChart;

        public UserStatistics(int makeCount, int gameCount, String firstName, String lastName) {
            this.makeCount = makeCount;
            this.gameCount = gameCount;
            this.firstName = firstName;
            this.lastName = lastName;
            try {
                ThermometerPlot plot = new ThermometerPlot(createThermometerDataset());
                File chartFile = new File("dynamichart");
                JFreeChart chart = new JFreeChart(plot);
                ChartUtilities.saveChartAsPNG(chartFile, chart, 50, 50);
                thermoChart = new DefaultStreamedContent(new FileInputStream(chartFile), "image/png");
            } catch (Exception e) {
                logger.severe(e.getMessage());
            }
            .....
        }
        .....
    }

JSF页面如下所示

<h:form id="stats">
                    <p:dataTable  id="statsTable" var="user" value="#{statisticsBean.userStatistics}">
                        <p:column styleClass="textColumn">
                            <f:facet name="header">
                                <h:outputText value="Name" />
                            </f:facet>
                            <h:outputText value="#{user.firstName} #{user.lastName}"/>
                        </p:column>
                        ...
                        <p:column styleClass="imageColumn">
                            <f:facet name="header">
                                <h:outputText value="Luck Barometer"/>
                            </f:facet>
                            <p:graphicImage value="#{user.thermoChart}"/>
                        </p:column>
                    </p:dataTable>
   </h:form>

你能看到我做错了什么吗？

Answer 1

最好不要将图像保存到服务器，然后以某种方式链接到它。首选的解决方案是按需生成图像，并将其从servlet流式传输到客户机，并在JSF中注入指向servlet的链接(当然，带有用于生成图像的参数)，而不是指向预先生成的图像文件的链接。

Answer 2

我认为，将图表图像写入磁盘是导致问题的原因。请改用输出流。试试这样的东西，

    try {
        ThermometerPlot plot = new ThermometerPlot(createThermometerDataset());

    ByteArrayOutputStream baos = new ByteArrayOutputStream();

        JFreeChart chart = new JFreeChart(plot);
        ChartUtilities.writeChartAsPNG(baos, chart, 50, 50);
        thermoChart = new DefaultStreamedContent( new ByteArrayInputStream(baos.toByteArray()), "image/png");
    } catch (Exception e) {
        logger.severe(e.getMessage());
    }

它可能会解决你的问题。