Question

我有一个bean“Player”当我在selectOneMenu中选择一个值时，我想“切换”到数据库中匹配的bean。

我将豆子送回

中的选择菜单

public List<Player> getAllPlayers() { }

更新了此内容的下拉列表。

<h:selectOneMenu value="#{servicePlayer.myPlayer.combinedName}"
    converter="playerConverter" id="playerList">
    <f:selectItems value="#{servicePlayer.allPlayers}" var="player"
        itemLabel="#{player.combinedName}" itemValue="#{player.id}" />
</h:selectOneMenu>

但我仍然无法将ID发送到转换器。它将从播放器发送firstName。

@FacesConverter(value = "playerConverter")
public class PlayerConverter implements Converter {

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if (value == null) {
            return null;
        }

        long idValue;
        try {
            idValue = Long.parseLong(value);
        }
        catch (NumberFormatException ex)
        {
            return null;
        }

        ServicePlayer servicePlayer = context.getApplication()
                .evaluateExpressionGet(context, "#{servicePlayer}",
                        ServicePlayer.class);
        Player player = servicePlayer.getPlayerByID(idValue);
        return player;

    }

    @Override
    public String getAsString(FacesContext arg0, UIComponent arg1, Object value) {
        String string = null;
        if (value instanceof Player) {
            string = ((Player) value).getFirstName();
        }
        return string;
    }

}

public class ServicePlayer {

    private static final String PERSISTENCE_UNIT_NAME = "BowlingFacelets";
    public static EntityManagerFactory factory;
    Player myPlayer;

    public Player getMyPlayer() {
        return myPlayer;
    }


    public void setMyPlayer(Player myPlayer) {
        this.myPlayer = myPlayer;
    }


    public List<Player> getAllPlayers() {

        if (factory == null) {
            factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
        }

        EntityManager em = factory.createEntityManager();
        //Order by the matchdate.
        //Query q = em.createQuery("select t from DBTest t");
        Query q = em.createQuery("select t from Player t");

        List<Player> players = q.getResultList();
        for (Player aPlayer : players) {
          System.out.println(aPlayer);
        }
        System.out.println("Size: " + players.size());

        em.close();

        return players;
    }


public Player getPlayerByID(long id) {

        if (factory == null) {
            factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
        }

        EntityManager em = factory.createEntityManager();
        //Query q = em.createQuery("select t from Player t where t.name = '" + playerName + "'");
        //List<Player> players = q.getResultList();
        Player currentPlayer = em.find(Player.class, id);

        return currentPlayer;

    }


}

Answer 1

我认为你误解了selectOneMenu的value属性是指什么。它的用法就像在所有其他输入组件中一样，用于存储用户输入的位置（或从中获取现有值的位置）。

检查http://www.jsftoolbox.com/documentation/help/12-TagReference/core/f_selectItems.html。你需要根据f：select项的'var'属性设置键值和值对，否则JSF无法真正知道你想用Player对象做什么。

因此，键值/值对（键设置为值属性和值显示给用户的任何设置）就位，如果您使用player.id作为值，则可以获取基于该ID的用户。

Answer 2

JSF Converter负责将Object转换为itemValue属性的字符串值，然后从字符串值中恢复该Object。对于您的情况，对象是Player实体，而值是其ID的String表示（可能是其他任何内容，只要如你所知，它是唯一的）。

基本上，使用这个转换器：

@FacesConverter(value = "playerConverter")
public class PlayerConverter implements Converter {

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if (value == null) {
            return null;
        }

        long idValue;
        try {
            idValue = Long.parseLong(value);
        }
        catch (NumberFormatException ex)
        {
            return null;
        }

        ServicePlayer servicePlayer = context.getApplication()
                .evaluateExpressionGet(context, "#{servicePlayer}",
                        ServicePlayer.class);
        Player player = servicePlayer.getPlayerByID(idValue);
        return player;

    }

    @Override
    public String getAsString(FacesContext arg0, UIComponent arg1, Object value) {
        String string = null;
        if (value instanceof Player) {
            string = ((Player) value).getId();
        }
        return string;
    }

}

注意我更改了您通过ID 返回的名称。这样，作为玩家标识1，JSF知道它的字符串值是"1"。这是选择的值，它是通过getAsString方法获得的。

当您 POST 表单时，JSF必须从Player值恢复"1"实体，因此您使用Converter getAsObject从中加载<h:selectOneMenu value="#{servicePlayer.myPlayer.combinedName}" converter="playerConverter" id="playerList"> <f:selectItems value="#{servicePlayer.allPlayers}" var="player" itemLabel="#{player.combinedName}" itemValue="#{player}" /> </h:selectOneMenu> DB。

这样就可以从视图中引用对象本身，让jsf进行转换：

{{1}}

在JSF中选择“切换”bean的最佳方法

2 个答案: