我正在尝试做一些与应用程序引擎教程中的Guestbook非常相似的事情（开始）。然而，我想修改表单中字段的类型。Eclipse没有显示任何错误，但服务器显示：
Problem accessing /. Reason:
java.lang.NoSuchMethodError: prototipo2.Greeting.getDistance()Ljava/lang/Float;
Caused by:
javax.servlet.ServletException: java.lang.NoSuchMethodError: prototipo2.Greeting.getDistance() Ljava/lang/Float;
at org.apache.jasper.runtime.PageContextImpl.doHandle PageException(PageContextImpl.java:862)
at org.apache.jasper.runtime.PageContextImpl.handlePa geException(PageContextImpl.java:791)
at org.apache.jsp.prototipo2_jsp._jspService(prototip o2_jsp.java:326)
at org.apache.jasper.runtime.HttpJspBase.service(Http JspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:717)
at org.apache.jasper.servlet.JspServletWrapper.servic e(JspServletWrapper.java:377)
at org.apache.jasper.servlet.JspServlet.serviceJspFil e(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspSe rvlet.java:260)
at com.google.appengine.tools.development.PrivilegedJ spServlet.access$101 (PrivilegedJspServlet.java:23)
at com.google.appengine.tools.development.PrivilegedJ spServlet$2.run(PrivilegedJspServlet.java:59)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.PrivilegedJ spServlet.service(PrivilegedJspServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1166)
at com.google.appengine.tools.development.BackendServ ersFilter.doFilter(BackendServersFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:418)
at com.google.appengine.tools.development.DevAppEngin eWebAppContext.handle(DevAppEngineWebAppContext.ja va:78)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispa tcher.java:327)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispa tcher.java:126)
at com.google.appengine.tools.development.StaticFileU tils.serveWelcomeFileAsForward(StaticFileUtils.jav a:80)
at com.google.appengine.tools.development.LocalResour ceFileServlet.maybeServeWelcomeFile(LocalResourceF ileServlet.java:254)
at com.google.appengine.tools.development.LocalResour ceFileServlet.doGet(LocalResourceFileServlet.java: 120)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1166)
at com.google.appengine.tools.development.HeaderVerif icationFilter.doFilter(HeaderVerificationFilter.ja va:35)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFi lter.doFilter(ServeBlobFilter.java:60)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCle anupFilter.doFilter(TransactionCleanupFilter.java: 43)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileF ilter.doFilter(StaticFileFilter.java:122)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.BackendServ ersFilter.doFilter(BackendServersFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:418)
at com.google.appengine.tools.development.DevAppEngin eWebAppContext.handle(DevAppEngineWebAppContext.ja va:78)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContai nerService$ApiProxyHandler.handle(JettyContainerSe rvice.java:363)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.he aderComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run (QueuedThreadPool.java:582)
Caused by: java.lang.NoSuchMethodError: prototipo2.Greeting.getDistance()Ljava/lang/Float;
at org.apache.jsp.prototipo2_jsp._jspService(prototip o2_jsp.java:187)
... 56 more
我的代码是：
@Persistent
private Float distance;
public Greeting (User author, String content, Date date, String distance) {
this.author = author;
this.content = content;
this.date = date;
this.distance = Float.parseFloat(distance); }
}
public Float getDistance() {
return distance;
}
Eclipse说，当我运行应用程序时，一切都很好，但当我在本地主机域中打开文件时，我会看到我以前给你写的错误。
然而，如果我用这样的方式更改代码：
@Persistent
private String distance;
public Greeting (User author, String content, Date date, String distance) {
this.author = author;
this.content = content;
this.date = date;
this.distance = distance;
}
public String getDistance() {
return distance;
}
谢谢！
我认为您有两个问题：
-
某个地方有一个Long字段，其中的数据是一个字符串，无法转换为Long。
-
如果将
distance参数分配给浮点字段，为什么要将其转换为Integer？请改用Float.parseFloat(..)。
您得到的错误是从数据存储中读回已持久化的实体。看起来您已经存储了具有String属性的数据，您现在正试图将其读取到一个已将该属性重新定义为Long的实体中——您是否更改了ID字段的类型？