我对 gwt 还很陌生,弄清楚与 mysql 数据库的连接让我很难过。由于很少有直接的教程,我一直在这里讨论另一个 stackoverflow 问题。
http://stackoverflow.com/questions/8335322/java-gwt-mysql-connection-refused/8388422#8388422
虽然我不能正确。很少有事情,这个项目没有使用 GAE,只是 GWT,正如在另一个问题中的先前答案所建议的那样。是的,我可以通过另一个示例程序连接到我的数据库,所以到数据库的链接是打开的。我还将我的 mysql 驱动程序导入到 /WEB-INF/lib,并将其添加到我的 java 构建路径中。
关键是,我不知道为什么我无法连接,而且我的控制台也没用,如果有人能立即看到我做错了什么,那就太好了,或者如果有办法打印出更多的错误消息,这会很棒,而且我不知道如何查看服务器端资源的控制台(我在某处读到,错误可能比显示的更多?)谢谢。
这是我的 GreetingServiceImpl.java 相关代码
private final Connection connect() {
String driver = "com.mysql.jdbc.Driver";
String dblink = "jdbc:mysql://localhost:3306/";
String dbname = "gwttest";
String dbuser = "user";
String dbpass = "test";
try {
Class.forName(driver).newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Connection conn = null;
try {
conn = DriverManager.getConnection(dblink + dbname, dbuser, dbpass);
} catch (SQLException e) {
System.err.println("mysql connection error: ");
e.printStackTrace();
}
return conn;
}
这是我的 helloserver.java 相关代码
Button b = new Button("test");
vPanel.add(b);
b.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
GreetingServiceAsync testservice= (GreetingServiceAsync) GWT.create(GreetingService.class);
testservice.echo("test", new AsyncCallback<String>() {
@Override
public void onFailure(Throwable caught) {
// TODO Auto-generated method stub
vPanel.add(new Label("error"));
//vPanel.add(new Label(caught.printStackTrace());
caught.printStackTrace();
}
@Override
public void onSuccess(String result) {
// TODO Auto-generated method stub
vPanel.add(new Label(result));
}
});
}
});
这是我在运行并单击按钮时收到的错误消息(除了在我的 html 中弹出的“错误”)
com.google.gwt.user.client.rpc.StatusCodeException: 404 <html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"/>
<title>Error 404 NOT_FOUND</title>
</head>
<body><h2>HTTP ERROR: 404</h2><pre>NOT_FOUND</pre>
<p>RequestURI=/helloserver/greet</p><p><i><small><a href="http://jetty.mortbay.org/">Powered by Jetty://</a></small></i></p><br/>
</body>
</html>
at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:209)
at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:338)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:279)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:242)
at sun.reflect.GeneratedMethodAccessor23.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
at java.lang.Thread.run(Unknown Source)