[英]Best way to “switch” bean on selection in JSF
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。
我把豆子送回到了选择菜单中
public List<Player> getAllPlayers() { }
已将下拉菜单更新为此。
<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>
但是我仍然无法将其发送给转换器。 它将发送玩家的名字。
@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;
}
}
我认为您误解了selectOneMenu的value属性所指的是什么。 就像在所有其他输入组件中一样,它的用途是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 。 您将需要基于f:select项上的'var'属性设置键和值对,否则JSF无法真正知道您要对Player对象执行什么操作。
因此,考虑到键/值对(键进入您设置为value属性的任何值,并向用户显示值)的位置,并且例如,如果您使用player.id作为值,则可以基于在那个ID上。
JSF Converter
的工作是将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, Object是Player
实体,而值是其id的String
表示形式(可以是其他任何形式,只要您知道它是唯一的即可 )。
基本上,使用此转换器:
@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;
}
}
请注意, 我通过id更改了您要返回的名称 。 这样,作为玩家ID 1
,JSF知道该字符串的值为"1"
。 这就是选择的值,它是通过getAsString
方法获得的。
POST表单时,JSF必须从"1"
值恢复Player
实体,因此您可以使用Converter的getAsObject
从数据库中加载它。
这样,从视图中引用对象本身就足以让jsf进行转换:
<h:selectOneMenu value="#{servicePlayer.myPlayer.combinedName}"
converter="playerConverter" id="playerList">
<f:selectItems value="#{servicePlayer.allPlayers}" var="player"
itemLabel="#{player.combinedName}" itemValue="#{player}" />
</h:selectOneMenu>
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