使用 Glassfish4 的 servlet (JavaEE) 中的 IllegalArgumentException

Question

我有一个 servlet，用于检索存储在 JavaEE 数据库中的用户。

当我调用 servlet 时，我从 Glassfish4 收到以下错误

type: Exception report

message: Internal Server Error

description: The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Error instantiating servlet class com.storassa.javaee.scuolatennis.nicola.GetPlayersApi

root cause

com.sun.enterprise.container.common.spi.util.InjectionException: Error creating managed object for class: class com.storassa.javaee.scuolatennis.nicola.GetPlayersApi

root cause

com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting to inject Local ejb-ref name=com.storassa.javaee.scuolatennis.nicola.GetPlayersApi/playerEjb,Local 3.x interface =com.storassa.javaee.scuolatennis.nicola.PlayerEJB resolved to intra-app EJB PlayerEJB in module scuolatennisnicola-0.0.1-SNAPSHOT,ejb-link=PlayerEJB,lookup=,mappedName=,jndi-name=,refType=Session into class com.storassa.javaee.scuolatennis.nicola.GetPlayersApi: Can not set com.storassa.javaee.scuolatennis.nicola.PlayerEJB field com.storassa.javaee.scuolatennis.nicola.GetPlayersApi.playerEjb to com.storassa.javaee.scuolatennis.nicola.GetPlayersApi

root cause

java.lang.IllegalArgumentException: Can not set com.storassa.javaee.scuolatennis.nicola.PlayerEJB field com.storassa.javaee.scuolatennis.nicola.GetPlayersApi.playerEjb to com.storassa.javaee.scuolatennis.nicola.GetPlayersApi

消息似乎表明 servlet 已分配给 EJB，但这怎么会发生呢？还是我误解了消息？

奇怪的是，在显示此错误消息后，如果我再次尝试重新加载页面，则会返回 404 消息，就好像 servlet 已从应用程序中“取消部署”一样，并且是再次看到相同错误的唯一方法消息是重新部署应用程序。 这是 servlet：

<imports...>

/**
 * Servlet implementation class GetPlayersApi
 * 
 * The API is the following: if nothing is present retrieves all the players if
 * ordered=true, retrieves all the players ordered if email=<email> retrieve the
 * player with the given email
 */
@WebServlet("/api/getPlayers")
public class GetPlayersApi extends HttpServlet {
    private static final long serialVersionUID = 1L;

    // The list of the News to store the query in the DB
    List<Player> players;

    // Inject the News bean to get the data from DB
    @EJB
    PlayerEJB playerEjb;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public GetPlayersApi() {
        super();
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // get the map of the request parameters
        HashMap<String, String[]> map = (HashMap<String, String[]>) request.getParameterMap();

        // if no parameters are given
        if (map.size() == 0)
            // retrieve all the tags currently in the DB
            players = playerEjb.findPlayers();

        // else if ordered=true
        else if (map.get("ordered") != null && map.get("ordered")[0] == "true") {

            // get the Players in social ranking order
            players = playerEjb.findRankingOrderedPlayers();

        } else {

            String email = request.getParameter("email");
            Player player = playerEjb.findPlayerFromEmail(email);
            if (player != null)
                players.add(player);

        }

        // convert the result in JSON format and put them in the response
        JSONArray array = new JSONArray(players);
        response.getWriter().append(array.toString());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

    public PlayerEJB getPlayerEJB() {
        return playerEjb;
    }

    public void setPlayerEJB(PlayerEJB pl) {
        playerEjb = pl;
    }

}

这是 PlayerEJB 类

@LocalBean
@Stateless
public class PlayerEJB {
    // Inject the EntityManager to persist the LocationData entity
    @PersistenceContext(unitName = "scuolaTennisNicolaPU")
    private EntityManager em;

    /**
     * This method return the list of Player entities currently stored in the DB
     * 
     * @return a List of News objects
     */
    public List<Player> findPlayers() {
        Query query = em.createNamedQuery("findAllPlayers");
        return query.getResultList();
    }

    /**
     * This method retrieves from the DB the persisted player with the given
     * email
     * 
     * @param email
     *            the email of the player to be retrieved from the DB
     * @return the player with the given email that was persisted in the DB
     */
    public Player findPlayerFromEmail(String email) {

        // create the query
        String s = "SELECT p FROM Player p WHERE p.email = '" + email + "'";
        Query query = em.createQuery(s);

        // query the DB
        List<Player> list = (List<Player>) query.getResultList();
        // if the list is not empty return the first item in the list
        if (list.size() > 0)
            return list.get(0);
        else
            return null;
    }

    /**
     * This method return the list of Player entities currently stored in the DB
     * in social ranking order
     * 
     * @return a List of News objects
     */
    public List<Player> findRankingOrderedPlayers() {
        Query query = em.createNamedQuery("findAllPlayersInRankingOrder");
        return query.getResultList();
    }

    /**
     * This method remove all the Player entities currently stored in the DB
     */
    public void removePlayers() {
        Query query = em.createNamedQuery("removeAllPlayers");
        query.executeUpdate();
    }

    /**
     * This method remove the Player entities currently stored in the DB with a
     * given name and surname;
     * 
     * @param name
     *            the name of the player to be deleted
     * @param surname
     *            the surname of the player to be deleted
     */
    public void removePlayersWithName(String name, String surname) {
        // create the query
        String s = "DELETE FROM Player p WHERE p.name = '" + name + "' AND p.surname = '" + surname + "'";
        Query query = em.createQuery(s);

        query.executeUpdate();
    }

    /**
     * This method remove the Player entities currently stored in the DB with a
     * given name and surname;
     * 
     * @param name
     *            the name of the players to be deleted
     * @param surname
     *            the surname of the players to be deleted
     */
    public void removePlayersWithName(String[] name, String[] surname) {

        if (name.length != surname.length)
            throw new IllegalArgumentException("The two arrays arae not of the same length");
        // create the query
        for (int i = 0; i < name.length; i++) {
            String s = "DELETE FROM Player p WHERE p.name = '" + name[i] + "' AND p.surname = '" + surname[i] + "'";
            Query query = em.createQuery(s);

            query.executeUpdate();
        }
    }

    /**
     * This method remove the Player entities currently stored in the DB with a
     * given name and surname;
     * 
     * @param name
     *            the name of the players to be deleted
     * @param surname
     *            the surname of the players to be deleted
     */
    public void updatePlayersWithEmail(Player player) {

        if (player == null)
            throw new IllegalArgumentException("Argument cannot be null");

        String[] parts = { "p.name", "p.surname", "p.password", "p.age", "p.officialRanking", "p.phone", "p.email", "p.emailChallenger", "p.socialRanking",
                "p.role" };

        for (int i = 0; i < parts.length; i++) {
            String queryString = "UPDATE Player p SET " + parts[i] + "WHERE p.email = '" + player.getEmail();
            Query query = em.createQuery(queryString);
            query.executeUpdate();
        }
    }

    /**
     * This method persist a Player entity
     * 
     * @param data
     *            The Player entity to be persisted
     * @return the same Player entity that has just been persisted
     */
    public Player createPlayer(Player data) {
        em.persist(data);
        return data;
    }

}

Answer 1

根据 OP 上的 cmets，我们已将问题缩小到 @PersistenceContext EntityManager 未注入 PlayerEJB。

如果没有额外的信息，很难说出确切的问题是什么，但很可能是以下问题之一：

• 确保unitName scuolaTennisNicolaPU 对应于META-INF/persistence.xml 中定义的persistenceUnit 例如：
  <persistence-unit name="scuolaTennisNicolaPU">
• 早先在日志中查看注入 EntityManager 的问题是什么，这是根本问题，而不是 EJB 无法注入 Servlet 的事实。
• 确保您的 EJB 使用位于 META-INF 目录中的 beans.xml 打包。

---

如果这些方法都不能解决您的问题，则需要更多信息，请尝试更新您的问题：

• 早期的异常消息表明为什么 EntityManager 未能注入 PlayerEJB。
• 您的persistence.xml 配置