将连接返回到池

Question

我有一个JSF 2.0页面，用户可以在其中登录，他可以选择注销（令人惊讶）。我的JBoss服务器配置最多允许7个线程（连接）。我与一位用户测试了几次页面登录，然后尝试进行7次尝试Transaction not active，这也许意味着注销后连接不会重新回到池中并保持打开状态。

问：注销和返回线程池中的线程的方法是什么？这个问题困扰了我很长时间。请帮忙。

这是我的JBoss中standalone.xml用于限制连接的数据源的配置：

<subsystem xmlns="urn:jboss:domain:datasources:1.0">
            <datasources>
                <datasource jndi-name="java:jboss/MyJndiDS" pool-name="MyPoolDS" enabled="true" jta="true" use-java-context="false" use-ccm="true">
                    <connection-url>
                        jdbc:postgresql://192.168.2.125:5432/t_report
                    </connection-url>
                    <driver>
                        org.postgresql
                    </driver>
                    <transaction-isolation>
                        TRANSACTION_READ_COMMITTED
                    </transaction-isolation>
                    <pool>
                        <min-pool-size>
                            3
                        </min-pool-size>
                        <max-pool-size>
                            7
                        </max-pool-size>
                        <prefill>
                            true
                        </prefill>
                        <use-strict-min>
                            false
                        </use-strict-min>
                        <flush-strategy>
                            FailingConnectionOnly
                        </flush-strategy>
                    </pool>
                    <security>
                        <user-name>
                            my_user
                        </user-name>
                        <password>
                            my_pass
                        </password>
                    </security>
                    <statement>
                        <prepared-statement-cache-size>
                            32
                        </prepared-statement-cache-size>
                    </statement>
                </datasource>
...
...
            </datasources>
</subsystem>

和在注销方法@SessionScoped类

import javax.faces.context.ExternalContext;
...
...
@Inject ExternalContext ec;

public void validateUserLogOut() {

    HttpServletRequest request = (HttpServletRequest)ec.getRequest();
    request.getSession().invalidate();
    this.setUserLoggedIn(false);
    navigation.logout();

}

编辑：这是用户登录的方式。希望这会有所帮助。

public void validateLogUser() {
    ResourceBundle bundle = ResourceBundle.getBundle("internationalization.language", context.getViewRoot().getLocale());
    String validation = logUser();
    if((validation == null) || validation.isEmpty()) {
        context.addMessage(null,
            new FacesMessage(FacesMessage.SEVERITY_WARN,
            bundle.getString("wrongUsername"),bundle.getString("wrongUsername")));
    } else if (validation == "welcome") {
        this.setUserLoggedIn(true);
        navigation.login();
    }
}

哪里logUser()是：

public synchronized String logUser() {

    try {
        EntityManagerUtil.getEntityManager().getTransaction().begin();
        System.out.println(user);
        if(user.getUsername().isEmpty() || (user.getUsername() == null)) {
            return null;
        }
        String password = user.getPassword();
        user = (UserBean) EntityManagerUtil.getEntityManager().find(UserBean.class, user.getUsername());
        if(user == null) {
            HttpServletRequest request = (HttpServletRequest)ec.getRequest();
            request.getSession().invalidate();
        }
        if(user.getPassword().equals(password)) {
            log.info("User: " + user.getUsername() + " logged successfully.");
            return "welcome";
        } else {
            HttpServletRequest request = (HttpServletRequest)ec.getRequest();
            request.getSession().invalidate();
            return null;
        }
    } catch (Exception e) {
        log.error("Error while logging in : \n\t" + e);
        EntityManagerUtil.getEntityManager().getTransaction().rollback();
        return null;  
    } finally {
        EntityManagerUtil.close();
    }
}

这是如何EntityManagerUtil.getEntityManager()工作的：

 /**
 * ThreadLocal instance that holds unique EntityManager per thread, 
 * it means that every thread accessing this ThreadLocal will has it's own instance of EntityManager
 */
private static final ThreadLocal<EntityManager> entitymanager = 
    new ThreadLocal<EntityManager>();

 /**
 * @param persistenceUnit - String name of the persistece unit 
 *  to be used as declared inside persistence.xml
 * @return singleton instance of EntityManagerFactory
 */
public synchronized static EntityManagerFactory initializeEntityManagerFactory( String persistenceUnit ) {
    if ( entityManagerFactory == null ) {
        // Create the EntityManagerFactory
        entityManagerFactory = Persistence.createEntityManagerFactory( persistenceUnit );
    }
    return entityManagerFactory;
}


 /**
 * @return Singleton instance of EntityManager per Thread
 */
public static EntityManager getEntityManager() {
    initializeEntityManagerFactory( "MyPersistenceUnit" );
    EntityManager entityManager = entitymanager.get();

    // Create a new EntityManager
    if ( entityManager == null) {
        entityManager = entityManagerFactory.createEntityManager();
        entitymanager.set( entityManager );
    }

    return entityManager;
}


/**
 * Close all ThreadLocals
 */
public static void close() {
    final EntityManager entityManager = entitymanager.get();
    entitymanager.set( null );
    if ( entityManager != null && entityManager.isOpen()) { 
        entityManager.close();
    }
    if ( entityManagerFactory != null && entityManagerFactory.isOpen()) {
        entityManagerFactory.close();
    }
}

Answer 1

您正在重新发明轮子。请通过在容器管理的实体管理器中添加@PersistenceContext注解并EJB管理交易来使用它。这将容易得多，并且出错的可能性也较小。

这是一个简单的DAO：

@Stateless
public class UserDAO {

   @PersistenceContext
   private EntityManager entityManager;

   public void insertUser(User user) {
      entityManager.persist(user); 
   }
}

默认情况下，中的每个方法EJB都是事务性的。您可以使用@TransactionAttribute注释实现细粒度的控制。真的很简单。