support spring Jdbc4NativeJdbcExtractor

src/main/java/com/alibaba/druid/proxy/jdbc/PreparedStatementProxyImpl.java

@@ -54,7 +54,7 @@ public class PreparedStatementProxyImpl extends StatementProxyImpl implements Pr
         return this.sql;
     }
 
-    public PreparedStatement getRawPreparedStatement() {
+    public PreparedStatement getRawObject() {
         return this.statement;
     }
 
@@ -342,4 +342,13 @@ public class PreparedStatementProxyImpl extends StatementProxyImpl implements Pr
     public String getLastExecuteSql() {
         return this.sql;
     }
+    
+    @SuppressWarnings("unchecked")
+    public <T> T unwrap(Class<T> iface) throws SQLException {
+        if (iface == PreparedStatement.class) {
+            return (T) statement;
+        }
+        
+        return super.unwrap(iface);
+    }
 }