Question

我在使用eclipse的java中使用Google App引擎时有一个奇怪的编译问题。当我尝试GWT编译我的代码时，我收到如下错误：

Compiling module beer.SQLBeer
   Validating newly compiled units
      Ignored 1 unit with compilation errors in first pass.
Compile with -strict or with -logLevel set to TRACE or DEBUG to see all errors.
   Finding entry point classes
      [ERROR] Errors in 'file:/C:/Users/Mark/workspace/SQLBeer/src/beer/client/SQLBeer.java'
         [ERROR] Line 12: The import com.google.appengine.api.rdbms cannot be resolved
         [ERROR] Line 13: The import com.google.apphosting cannot be resolved
         [ERROR] Line 14: The import com.google.cloud cannot be resolved
         [ERROR] Line 18: ServersServlet cannot be resolved to a type
         [ERROR] Line 22: The method doPost(HttpServletRequest, HttpServletResponse) of type SQLBeer must override or implement a supertype method
         [ERROR] Line 26: Connection cannot be resolved to a type
         [ERROR] Line 28: AppEngineDriver cannot be resolved to a type
         [ERROR] Line 29: Connection cannot be resolved to a type
      [ERROR] Unable to find type 'beer.client.SQLBeer'
         [ERROR] Hint: Previous compiler errors may have made this type unavailable
         [ERROR] Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly
Exception in thread "UnitWriteThread"

我不确定为什么它无法解决导入，这阻止我将我的代码部署到Google应用引擎上。我觉得因为它与我的导入效果不佳所以我得到错误的原因相同

[ERROR] Line 22: The method doPost(HttpServletRequest, HttpServletResponse) of type SQLBeer must override or implement a supertype method

我真的很擅长使用GWT和Google App Engine for Eclipse，但我试图访问我的团队使用Google Cloud SQL创建的数据库。我觉得我越来越接近，如果我能克服这些错误。

项目代码

package beer.client;


import java.io.IOException;
import java.io.PrintWriter;
import java.sql.DriverManager;
import java.sql.SQLException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.appengine.api.rdbms.AppEngineDriver;
import com.google.apphosting.utils.servlet.ServersServlet;
import com.google.cloud.sql.jdbc.Connection;


@SuppressWarnings("serial")
public class SQLBeer extends ServersServlet {


    @Override 
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {

        PrintWriter out = resp.getWriter();
        Connection c = null;
        try {
            DriverManager.registerDriver(new AppEngineDriver());
            c = (Connection) DriverManager
                    .getConnection("jdbc:google:rdbms://asu.edu:cst433team1:team1db/mysql");
            String fname = req.getParameter("fname");
            String content = req.getParameter("content");

            /**
             * This code appears to do the web form fun
             */
//          if (fname == "" || content == "") {
//              out.println("<html><head></head><body>You are missing either a message or a name! Try again! Redirecting in 3 seconds...</body></html>");
//          } else {
//              String statement = "INSERT INTO entries (guestName, content) VALUES( ? , ? )";
//              PreparedStatement stmt = c.prepareStatement(statement);
//              stmt.setString(1, fname);
//              stmt.setString(2, content);
//              int success = 2;
//              success = stmt.executeUpdate();
//              if (success == 1) {
//                  out.println("<html><head></head><body>Success! Redirecting in 3 seconds...</body></html>");
//              } else if (success == 0) {
//                  out.println("<html><head></head><body>Failure! Please try again! Redirecting in 3 seconds...</body></html>");
//              }
//          }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (c != null)
                try {
                    c.close();
                } catch (SQLException ignore) {
                }
        }
        //resp.setHeader("Refresh", "3; url=/beer.jsp");
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

    }

}

有关我可以采取哪些措施来解决这些错误？我尝试了不同的Imports，但它们似乎都导致了GWT编译器中的相同问题。

编辑：我将扩展更改为HttpServlet，现在错误有点不同

Compiling module beer.SQLBeer
   Validating newly compiled units
      Ignored 1 unit with compilation errors in first pass.
Compile with -strict or with -logLevel set to TRACE or DEBUG to see all errors.
   Finding entry point classes
      [ERROR] Errors in 'file:/C:/Users/Mark/workspace/SQLBeer/src/beer/client/SQLBeer.java'
         [ERROR] Line 13: The import com.google.appengine.api.rdbms cannot be resolved
         [ERROR] Line 14: The import com.google.cloud cannot be resolved
         [ERROR] Line 26: Connection cannot be resolved to a type
         [ERROR] Line 28: AppEngineDriver cannot be resolved to a type
         [ERROR] Line 29: Connection cannot be resolved to a type
      [ERROR] Unable to find type 'beer.client.SQLBeer'
         [ERROR] Hint: Previous compiler errors may have made this type unavailable
         [ERROR] Hint: Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly
Exception in thread "UnitWriteThread" java.lang.RuntimeException: Unable to read from byte cache

Answer 1

首先，检查这不是类路径问题 - 这意味着你没有在lib目录和类路径中拥有所有必需的jar。

如果失败，请确保此代码不是客户端（从您的软件包名称猜测），这将编译为javascript。您不希望这种情况发生在数据库连接代码中，因此您应该在服务器端使用此代码。

请参阅Client side上的文档＆amp; Server side代码。

Java中的GWT编译问题（Google App Engine）

1 个答案: