求助java.lang.NullPointerException
来源:百度知道 编辑:UC知道 时间:2024/05/16 14:58:09
HTTP Status 500 -
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type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause
java.lang.NullPointerException
hospital.db.dboperation.Doctor.checkUser(Doctor.java:195)
hospital.db.dboperation.DBOperation.<init>(dboperation.java:32)
hospital.db.dboperation.Doctor.<init>(Doctor.java:25)
org.apache.jsp.doctor.login_jsp._jspService(login_jsp.java:98)
org.
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type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause
java.lang.NullPointerException
hospital.db.dboperation.Doctor.checkUser(Doctor.java:195)
hospital.db.dboperation.DBOperation.<init>(dboperation.java:32)
hospital.db.dboperation.Doctor.<init>(Doctor.java:25)
org.apache.jsp.doctor.login_jsp._jspService(login_jsp.java:98)
org.
你引用了一个空对象
可能有一个对象 需要么个条件后才能使用 如果没有达到这个条件 你就使用它
这时就会产生这个异常 NullPointerException
出现这个情况的原因很多,都是野指针的错误类型
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