tomcat servlet连接mysql时出现问题如何排查

Question

Tomcat servlet 使用 getConnection() 连接到 mysql。只需从 db test table shop 中获取数据。与 mysql 的连接成功，但浏览器仍不显示来自后端的任何数据。 JavaScript 显示 request.status 为 200，request.readyState 为 2 或 3。我怎样才能找到问题？我什至没有在 tomcat 日志文件中看到任何异常。

public void doGet(HttpServletRequest request, HttpServletResponse response) 
    throws IOException, ServletException {
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");

        PrintWriter out = response.getWriter();
        out.println("ok");

        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "***");
            Statement statementQuery = connection.createStatement();

            ResultSet set = statementQuery.executeQuery("select * from shop");

            // connection.commit();  Error appears here(should be commented): 
            out.println("<div>");
            while (set.next()) {
                out.println("ok");
                out.println(set.getInt(1) + " ");
                out.println(set.getString(2) + " ");
                out.println(set.getDouble(3));          
            }
        } catch (Exception e) {

            e.printStackTrace();
        }
        out.println("</div>");

        out.flush();
        out.close();    
}

public void doPost(HttpServletRequest request, HttpServletResponse response) 
    throws IOException, ServletException {
        doGet(request, response);
}

编辑：
connection.commit() 是错误的。评论那一行，它就可以工作了。

Answer 1

把Oracle驱动改成Mysql驱动

Class.forName("com.mysql.jdbc.Driver");

SQL 语句按顺序执行。将执行顺序改为：

int ret = statement.executeUpdate("insert into shop values  (53, 'fjd', 43.2)"); 
ResultSet s1 = statement.executeQuery("select * from shop");

在连接上也执行一次提交

connection.commit();

并添加finally 以关闭statement 和connection

}finally{
    statement.close();
    connection.close();
}