Jboss EAP 6 EJB调用常见问题

1. 调用EJB的三种方法

调用EAP 6 EJB的第一种方法，使用JBoss API，如下：

Properties p = new Properties();
p.put("remote.connectionprovider.create.options.org.xnio.Options.SSL_ENABLED", "false");
p.put("remote.connections", "default");
p.put("remote.connection.default.host", "localhost");
p.put("remote.connection.default.port", "4447");
p.put("remote.connection.default.connect.options.org.xnio.Options.SASL_POLICY_NOANONYMOUS", "false");

EJBClientConfiguration cc = new PropertiesBasedEJBClientConfiguration(p);
ContextSelector<EJBClientContext> selector = new ConfigBasedEJBClientContextSelector(cc);
EJBClientContext.setSelector(selector);

Properties props = new Properties();
props.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming");
InitialContext context = new InitialContext(props);

final boolean useScopedExample = Boolean.getBoolean("UseScopedContext");
final String rcal = "ejb:jboss-ejb-multi-server-app-main/ejb//" + (useScopedExample ? "MainAppSContextBean" : "MainAppBean") + "!" + MainApp.class.getName();
final MainApp remote = (MainApp) context.lookup(rcal);

这种方法在Standalone client (client is not running inside of JBoss EAP 6)能正常调用，但在EAP 6环境中会报java.lang.SecurityException: EJBCLIENT000021: EJB client context selector may not be changed。

 

第二种方法使用scoped context，代码如下：

Properties props = new Properties();
props.put("org.jboss.ejb.client.scoped.context", "true");
props.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming");
//props.put(Context.OBJECT_FACTORIES, "org.jboss.ejb.client.naming.ejb.ejbURLContextFactory");
props.put("remote.connectionprovider.create.options.org.xnio.Options.SSL_ENABLED", "false");
props.put("remote.connections", "default");
props.put("remote.connection.default.port", 4447);
props.put("remote.connection.default.host", host);
//props.put("remote.connection.default.username", username);
//props.put("remote.connection.default.password", password);
props.put("remote.connection.default.connect.options.org.xnio.Options.SASL_POLICY_NOPLAINTEXT", "false");
props.put("jboss.naming.client.connect.options.org.xnio.Options.SASL_POLICY_NOPLAINTEXT", "false");

Context context = (Context) new InitialContext(props).lookup("ejb:");
try {
   final TimerExample bean = (TimerExample) context.lookup("TestTimer/TestTimerEJB/TimerExampleBean!org.example.jboss.timer.TimerExample");
   bean.doSomething();
} finally {
   try { 
       context.close();
   } catch(Exception e) { }
} 

这种方式，可以完全通过代码实现配置，但由客户端来创建和管理Connection，因此需要更多的资源，性能不高。还有一个严重的问题，当使用CMT，事物跨多个EJB时，因每次调用EJB后都关闭context（如不close，connection会一直保持），这将造成事务commit/rollback失败。这种情况下，就得使用第三种方式，也是推荐的方式：

先来看代码：

Properties props = new Properties();
props.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming");
final Context context = new javax.naming.InitialContext(props);
final Greeter bean = (Greeter) context.lookup("ejb:myapp/myejb/GreeterBean!" + org.myapp.ejb.Greeter.class.getName());
bean.doSometing();

 代码很简单，注意没有调用close()方法。那这是怎么找到远程主机的呢？需要增加一些配置，先在war的WEB-INF或ear的META-INF中新建一个文件jboss-ejb-client.xml，内容如下：

<jboss-ejb-client xmlns="urn:jboss:ejb-client:1.2">
    <client-context>
        <ejb-receivers>
            <remoting-ejb-receiver outbound-connection-ref="remote-ejb-connection-app1" connect-timeout="10000"/>
            <remoting-ejb-receiver outbound-connection-ref="remote-ejb-connection-app2" connect-timeout="10000"/>
        </ejb-receivers>
    </client-context>
</jboss-ejb-client>

 然后在standalone.xml增加如下配置，建立与远程主机的关联：

<subsystem xmlns="urn:jboss:domain:remoting:1.2">
    <connector name="remoting-connector" socket-binding="remoting" security-realm="ApplicationRealm"/>
    <outbound-connections>
        <remote-outbound-connection name="remote-ejb-connection-app1" outbound-socket-binding-ref="remote-ejb-app1">
            <properties>
                <property name="SASL_POLICY_NOANONYMOUS" value="false"/>
                <property name="SSL_ENABLED" value="false"/>
            </properties>
        </remote-outbound-connection>
        <remote-outbound-connection name="remote-ejb-connection-app2" outbound-socket-binding-ref="remote-ejb-app2">
            <properties>
                 <property name="SASL_POLICY_NOANONYMOUS" value="false"/>
                 <property name="SSL_ENABLED" value="false"/>
            </properties>
        </remote-outbound-connection>
    </outbound-connections>
</subsystem>

...

<socket-binding-group name="standard-sockets" default-interface="public" port-offset="${jboss.socket.binding.port-offset:0}">
    <outbound-socket-binding name="remote-ejb-app1">
        <remote-destination host="localhost" port="4447"/>
    </outbound-socket-binding>
    <outbound-socket-binding name="remote-ejb-app2">
        <remote-destination host="localhost" port="4447"/>
    </outbound-socket-binding>
</socket-binding-group>

 调用EJB后，来查看一下connection情况：netstat -aon | findstr "4447"（netstat -np | grep 4447）

 

2. Could not register a EJB receiver: java.lang.RuntimeException: Operation failed with status WAITING

 

EJB调用配置中包含以下三个timeout参数：

• invocation.timeout

The timeout for the EJB handshake or method invocation request/response cycle. The value is in milliseconds.
The invocation of any method throws a java.util.concurrent.TimeoutException if the execution takes longer than the timeout period. The execution completes and the server is not interrupted.

 

• reconnect.tasks.timeout

The timeout for the background reconnect tasks. The value is in milliseconds.
If a number of connections are down, the next client EJB invocation will use an algorithm to decide if a reconnect is necessary to find the right node.

 

• remote.connection.CONNECTION_NAME.connect.timeout

The timeout period for the initial connection. After that, the reconnect task will periodically check whether the connection can be established. The value is in milliseconds.

 

remote.connection.CONNECTION_NAME.connect.timeout默认值为5000ms(参见代码InitialContextFactory.getInitialContext)，当在timeout时间内连接不上时，就会报以上错误。

 

3. 关于Rollback

EJB方法抛出RuntimeException会引起rollback，那有方法指定某个Exception是否引起Rollback么？可以使用注解@ApplicationException，如下：

 

@ApplicationException(rollback = true)

public class MyException extends Exception {
    // ...
}

 

4. How to close scoped EJB client contexts?

Internally, when a lookup happens for a ejb: URL string, a relevant javax.naming.Context is created for that ejb: lookup.

So we first create a JNDI context and then use it to lookup an EJB.

final Properties props = new Properties();
// mark it for scoped EJB client context
props.put("org.jboss.ejb.client.scoped.context","true");
// add other properties
props.put(....);
...
Context jndiCtx = new InitialContext(props);
Context ejbRootNamingContext = (Context) jndiCtx.lookup("ejb:");
try {
    final MyBean bean = ejbRootNamingContext.lookup("app/module/distinct/bean!interface"); // rest of the EJB jndi lookup string
    bean.doSomething();
} finally {
    try {
        // close the EJB naming JNDI context
        ejbRootNamingContext.close();
    } catch (Throwable t) {
        // log and ignore
    }
    try {
        // also close our other JNDI context since we are done with it too
        jndiCtx.close();
    } catch (Throwable t) {
        // log and ignore
    }
 
}

 

Invoking Session Beans

Scoped EJB client contexts

How to configure an EJB client in JBoss EAP 6