这是我知道的测试查询,并返回14。
private static final String TEST = "SELECT album_id FROM Album";
每次执行以下方法时,都会抛出异常并返回变量x而不是我的album_id
public String getAlbumId(String email, String album_name) {
PreparedStatement stmt = null;
Connection conn = null;
ResultSet rs = null;
try{
conn = DbConnection.getConnection();
stmt = conn.prepareStatement(TEST);
//stmt.setString(1, email);
//stmt.setString(2, album_name);
rs = stmt.executeQuery();
String album_id = rs.getString(1);
return album_id;
}
catch(SQLException e) { String x="-1"; return x; }
}
调用此方法的jsp代码部分如下:
<table>
<%
AlbumDao album2 = new AlbumDao();
String myid;
int actualid;
for(String item : album_names) {
myid = album2.getAlbumId(email,item);
actualid = Integer.parseInt(myid);
System.out.println(myid);
%>
<tr>
<td><a href="display_album.jsp?album_id=<%=actualid%>"><% out.print(item);%></a></td>
</tr>
<%}%>
到目前为止,我已经看过几十次代码了,我无法弄明白。出现这种情况的原因是什么?
printStackTrace()的输出如下(抱歉长输出):
org.postgresql.util.PSQLException: ResultSet not positioned properly, perhaps you need to call next.
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.checkResultSet(AbstractJdbc2ResultSet.java:2452)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.getString(AbstractJdbc2ResultSet.java:1882)
at org.apache.tomcat.dbcp.dbcp.DelegatingResultSet.getString(DelegatingResultSet.java:174)
at photoshare.AlbumDao.getAlbumId(AlbumDao.java:66)
at org.apache.jsp.index_jsp._jspService(org.apache.jsp.index_jsp:103)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:524)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:667)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)
答案 0 :(得分:2)
您需要在rs.next()
之前致电rs.getString(1)
。例外情况也暗示相同。