add SpringNamespaceExample for XA.

sharding-jdbc-example/transaction-example/transaction-2pc-xa-example/transaction-xa-spring-namespace-example/src/main/java/io/shardingsphere/example/transaction/xa/spring/namespace/SpringNamespaceExample.java

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.shardingsphere.example.transaction.xa.spring.namespace;
+
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+public class SpringNamespaceExample {
+    
+    private static final String CONFIG_FILE = "META-INF/application-sharding-databases-tables.xml";
+    
+    public static void main(final String[] args) {
+        try (ConfigurableApplicationContext applicationContext = new ClassPathXmlApplicationContext(CONFIG_FILE)) {
+            XATransactionalService transactionalService = applicationContext.getBean(XATransactionalService.class);
+            transactionalService.initEnvironment();
+            transactionalService.processSuccess();
+            transactionalService.cleanEnvironment();
+        }
+    }
+}