【发布时间】：2014-09-14 05:15:07
【问题描述】：
我的 .jsp 文件：
<%@page import="lm.BookBean"%>
<%@page contentType="text/html"%>
<%@page pageEncoding="UTF-8"%>
<%@page import="java.sql.*"%>
<%@ page import="java.io.*,java.util.*,java.sql.*"%>
<%@ page import="javax.servlet.http.*,javax.servlet.*" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Library Settings</title>
</head>
<body>
<jsp:useBean id="book" scope="page" class="lm.BookBean" />
<%book.addSettings(); %>
</body>
</html>
我的 BookBean 是：
public int addSettings() {
System.out.println("step 1");
Connection con=null;
PreparedStatement ps=null;
try {
con=Database.getConnection();
ps=con.prepareStatement("insert into settings values (?,?,?)");
ps.setInt(1, no_of_books)
ps.setInt(2, day_renewal);
ps.setInt(3, fine);
ps.executeUpdate();
} catch(Exception e) {
e.printStackTrace();
} finally {
Database.clean(con, ps);
}
return (Integer) null;
}
我遇到了这种错误：
HTTP Status 500 - 类型异常报告消息描述服务器遇到内部错误（）
这阻止了它完成这个请求。
例外：
org.apache.jasper.JasperException: An exception occurred processing JSP page /LRapplication/pages/library_settings.jsp
at line 17 <jsp:useBean id="book" scope="page" class="lm.BookBean" />
<jsp:setProperty name="book" property="*"/> <%book.addSettings(); %>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:519)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:428)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:410)
...
org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515) root
cause
java.lang.NullPointerException
lm.BookBean.addSettings(BookBean.java:144)
org.apache.jsp.LRapplication.pages.library_005fsettings_jsp._jspService(library_005fsettings_jsp.java:87)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:386)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
...
【问题讨论】：