java - 打开起始页后未创建 SessionScoped bean

Question

您好，我是 jsf 的新手，遇到了这样的问题。我有这个代码的起始页:

<ui:repeat id="repeat" var="news" value="#{newsForm.newsList}">
    <div id="news-table">
        <div id="news-list-title">
            <h:outputText value="#{messages['body.news.title']}" />
            <h:outputText style="margin-left:10px;" value="#{news.newsTitle}" />
        </div>
        <div id="news-list-date">
            <h:outputText value="#{news.newsDate}">
                <f:convertDateTime pattern="dd/MM/yyyy" />
            </h:outputText>
        </div>
        <div id="news-list-brief">
            <h:outputText value="#{news.brief}" />
        </div>
    </div>
    <div id="links-style-area">
        <h:commandLink action="#{controller.view(news.id)}"
            value="#{messages['body.label.view']}" />
        <h:commandLink action="#{controller.edit(news.id)}"
            value="#{messages['body.label.edit']}" />
        <h:selectBooleanCheckbox id="checkbox"
            value="#{newsForm.checkboxes[news.id]}" />
    </div>
</ui:repeat>

我有 2 个托管 bean，一个是我的 Controller bean(用于删除、创建、更新新闻)，第二个用于在数据库 (newsForm) 中存储有关新闻的信息。所有 bean 都有 @SessionScoped 注释。 Controller bean 具有后构造函数，可以从数据库中获取所有新闻并将其设置到 newsForm bean 中。但是当我启动应用程序时，我看到空页面(因为我的 Controller bean 没有创建)。但是当我按下调用 Controller bean 方法的链接时，我在应用程序控制台中发现 Controller bean 已创建并且后构造函数已处理。

也许我错了，但我认为当 session 创建由 jsf 创建的所有 SessionScoped bean 时。

如果我错了请纠正我，或提供如何让我的应用程序在我打开起始页时显示所有新闻的建议。

更新

我在 Controller bean 中的 post 构造函数:

@PostConstruct
public void init() {
   try {
         list();
    } catch (NewsManagerException e) {
    }
}

列表方法:

public String list() throws NewsManagerException {
        newsForm.setNews(new News());
        newsForm.setCheckboxes(new HashMap<Integer, Boolean>());
        newsForm.setNewsList(newsDao.getNewsList());
        setAttribute(PREVIOUS_PAGE, LIST);
        return LIST;
    }

更新 2

这是 ControllerBean(这是 Struts 中 Action 类的模拟)

    public final class ControllerBean implements Serializable {
    private static final String PREVIOUS_PAGE = "previousPage";
    private static final String LIST = "news";
    private static final String EDIT = "edit";
    private static final String VIEW = "view";
    private static final String REDIRECT = "?faces-redirect=true";
    private final static Log log = LogFactory.getLog(ControllerBean.class);
    private INewsDao newsDao;
    private NewsBean newsForm;

    public ControllerBean() {
    }

    @PostConstruct
    public void init() {
        list();
    }

    public String list() {
        newsForm.setNews(new News());
        newsForm.setCheckboxes(new HashMap<Integer, Boolean>());
        try {
            newsForm.setNewsList(newsDao.getNewsList());
        } catch (NewsManagerException e) {
            log.error(e);
        }
        setAttribute(PREVIOUS_PAGE, LIST);
        return LIST;
    }

    public String add() {
        News news = new News();
        news.setNewsDate(new Date());
        newsForm.setNews(news);
        return EDIT;
    }

    private void setAttribute(String name, String value) {
        Map<String, Object> sessionMap = FacesContext.getCurrentInstance()
                .getExternalContext().getSessionMap();
        sessionMap.put(name, value);
    }

    private String getAttribute(String name) {
        Map<String, Object> sessionMap = FacesContext.getCurrentInstance()
                .getExternalContext().getSessionMap();
        return (String) sessionMap.get(name);
    }

    public String save() {
        int id = newsForm.getNews().getId();
        setAttribute(PREVIOUS_PAGE, VIEW);
        try {
            if (id == 0) {
                newsDao.createNews(newsForm.getNews());
                return VIEW;
            }
            newsDao.editNews(newsForm.getNews());
        } catch (NewsManagerException e) {
            log.error(e);
        }
        return VIEW;
    }

    public String edit(int id) {
        try {
            News news = newsDao.getNewsById(id);
            newsForm.setNews(news);
        } catch (NewsManagerException e) {
            log.error(e);
        }
        return EDIT;
    }

    public String view(int id) {
        try {
            setAttribute(PREVIOUS_PAGE, VIEW);
            newsForm.setNews(newsDao.getNewsById(id));
        } catch (NewsManagerException e) {
            log.error(e);
        }
        return VIEW;
    }

    public String cancel() {
        String page = getAttribute(PREVIOUS_PAGE);
        News news = newsForm.getNews();
        try {
            if (news.getId() != 0) {
                int id = news.getId();
                news = newsDao.getNewsById(id);
                newsForm.setNews(news);
            }
        } catch (NewsManagerException e) {
            log.error(e);
        }
        return page;
    }

    public String delete() {
        try {
            setAttribute(PREVIOUS_PAGE, LIST);
            Map<Integer, Boolean> allCheckboxes = newsForm.getCheckboxes();
            Set<Integer> checkboxes = newsForm.getCheckboxes().keySet();
            Set<Integer> checkedCheckboxes = new HashSet<>();
            for (Integer id : checkboxes) {
                boolean value = allCheckboxes.get(id);
                if (value) {
                    checkedCheckboxes.add(id);
                }
            }
            if (checkedCheckboxes.size() != 0) {
                newsDao.deleteNewsById(checkedCheckboxes.toArray());
            } else {
                Integer[] delete = { newsForm.getNews().getId() };
                newsDao.deleteNewsById(delete);
            }
            newsForm.setNewsList(newsDao.getNewsList());
        } catch (NewsManagerException e) {
            log.error(e);
        }
        return list() + REDIRECT;
    }

    public INewsDao getNewsDao() {
        return newsDao;
    }

    public void setNewsDao(INewsDao newsDao) {
        this.newsDao = newsDao;
    }

    public NewsBean getNewsForm() {
        return newsForm;
    }

    public void setNewsForm(NewsBean newsForm) {
        this.newsForm = newsForm;
    }

}

NewsBean(在 Struts 中用作 ActionForm 元素的简单 bean)

public final class NewsBean implements Serializable {
    private static final long serialVersionUID = 1L;
    private News news;
    private List<News> newsList;
    private Map<Integer, Boolean> checkboxes = new HashMap<>();

    public NewsBean() {
    }

    public News getNews() {
        return news;
    }

    public void setNews(News news) {
        this.news = news;
    }

    public List<News> getNewsList() {
        return newsList;
    }

    public void setNewsList(List<News> newsList) {
        this.newsList = newsList;
    }

    public Map<Integer, Boolean> getCheckboxes() {
        return checkboxes;
    }

    public void setCheckboxes(Map<Integer, Boolean> checkboxes) {
        this.checkboxes = checkboxes;
    }
}

映射

<managed-bean>
        <managed-bean-name>controller</managed-bean-name>
        <managed-bean-class>com.epam.newsmanagement.beans.ControllerBean</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
        <managed-property>
            <property-name>newsDao</property-name>
            <value>#{jpaDao}</value>
        </managed-property>
        <managed-property>
            <property-name>newsForm</property-name>
            <value>#{newsForm}</value>
        </managed-property>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>newsForm</managed-bean-name>
        <managed-bean-class>com.epam.newsmanagement.beans.NewsBean</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>

Answer 1

尝试使用 PrerenderView 而不是 post 构造:

从 ControllerBean 中删除 @postconstruct 并添加到您的页面中:

<f:metadata>
     <f:event type="preRenderView" listener="#{controller.init()}"/>
</f:metadata>