我有一个servlet，用于检索存储在JavaEE中的DB中的用户。
当我调用servlet时，我从Glassfish4中得到以下错误
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，但这怎么可能发生呢？或者我误解了这条消息？
奇怪的是，在显示此错误消息之后，如果我再次尝试重新加载页面，则返回404消息，就好像servlet是从应用程序“取消部署”并且只能再次查看相同的错误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;
}
}
答案 0 :(得分：0)
根据对OP的评论，我们已将问题范围缩小为@PersistenceContext EntityManager未注入PlayerEJB。
如果没有其他信息，很难说出确切的问题是什么，但可能是以下情况之一：
scuolaTennisNicolaPU对应于META-INF/persistence.xml中定义的persistenceUnit，例如：
<persistence-unit name="scuolaTennisNicolaPU"> EntityManager时出现的问题，这是根本问题，而不是EJB未能注入Servlet的事实。beans.xml位于META-INF目录中。如果这些问题都无法解决您的问题，则需要其他信息，请尝试使用以下方式更新您的问题：
EntityManager无法注入PlayerEJB的原因。persistence.xml配置