GWT连接数据库

在eclipse中安装好app engine与gwt插件后,就做了GWT连接数据库的测试,但是在APP engine中总是报错

java.security.AccessControlException access denied (java.net.SocketPermission localhost resolve)

就这个问题我提过问,没有人解决,具体的报错信息大家可以看这里http://www.iteye.com/problems/33692

查了下资料,google的官方文档上说在tomcat下,当servlet访问容器外部资源时,要时行授权,如果没有授权就会报没有权限的问题了.

于入进入tomcat-home/conf/catalina.policy,发现这个文件里面己经有了一些授权的声明如下:

grant codeBase "file:${java.home}/lib/-" {
        permission java.security.AllPermission;
};

 于是我就想是不是我的App Engine里面没有类似的授权呢,于是将GWT 项目打成war包发布到tomcat 下运行,没有任何问题.

GWT连接数据库代码:

public class UserListServiceImpl extends RemoteServiceServlet implements UserListService{
	public List<String> getUserList(){
		try {
//			Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver").newInstance();
//			Connection conn = DriverManager.getConnection("jdbc:sqlserver://localhost:1433;DatabaseName=zg", "sa", "sa");
			Class.forName("com.mysql.jdbc.Driver").newInstance();
			Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/hibernate", "root", "root");
			List<String> userList = new ArrayList<String>();
		     Statement stmt = null;
		     ResultSet rs = null;
		     try {
		       conn = DBConnection.getConnection();
		       stmt = conn.createStatement();
		       rs = stmt.executeQuery("select * from user");
		       while (rs.next()) {
		         userList.add(rs.getString(1) + "  " + rs.getString(2) + "  " + rs.getString(3));
		         System.out.println(rs.getString(1) + "  " + rs.getString(2) + "  " + rs.getString(3));
		       }
		     }
		     catch (SQLException e) {
		       e.printStackTrace();
		     }
		     return userList;
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		return null;
	}
	
}

 

与正常的数据库连接没有任何区别,关键是上面的访问权限的问题