add oracle visitor demo.

src/test/java/com/alibaba/druid/demo/sql/OracleVisitorDemo.java

@@ -0,0 +1,42 @@
+package com.alibaba.druid.demo.sql;
+
+import com.alibaba.druid.sql.SQLUtils;
+import com.alibaba.druid.sql.ast.SQLExpr;
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.ast.statement.SQLTableSource;
+import com.alibaba.druid.sql.dialect.oracle.ast.stmt.OracleSelectTableReference;
+import com.alibaba.druid.sql.dialect.oracle.visitor.OracleASTVisitorAdapter;
+import com.alibaba.druid.util.JdbcConstants;
+import junit.framework.TestCase;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class OracleVisitorDemo extends TestCase {
+    public void test_for_demo() throws Exception {
+        String sql = "select * from mytable a where a.id = 3";
+        List<SQLStatement> stmtList = SQLUtils.parseStatements(sql, JdbcConstants.ORACLE);
+
+        MyOracleVisitor visitor = new MyOracleVisitor();
+        for (SQLStatement stmt : stmtList) {
+            stmt.accept(visitor);
+        }
+
+        SQLTableSource tableSource = visitor.getAliasMap().get("a");
+        System.out.println(tableSource);
+    }
+
+    public static class MyOracleVisitor extends OracleASTVisitorAdapter {
+        private Map<String, SQLTableSource> aliasMap = new HashMap<String, SQLTableSource>();
+        public boolean visit(OracleSelectTableReference x) {
+            String alias = x.getAlias();
+            aliasMap.put(alias, x);
+            return true;
+        }
+
+        public Map<String, SQLTableSource> getAliasMap() {
+            return aliasMap;
+        }
+    }
+}