不能将值 NULL 插入列 'sno'，表 'student.dbo.home'；列不允许有 Null 值。INSERT 失败。

Question

在做jdbc（eclipse+sql server）的时候出现了
HTTP Status 500 - javax.servlet.ServletException: com.microsoft.sqlserver.jdbc.SQLServerException: 不能将值 NULL 插入列 'sno'，表 'student.dbo.home'；列不允许有 Null 值。INSERT 失败。

type Exception report

message javax.servlet.ServletException: com.microsoft.sqlserver.jdbc.SQLServerException: 不能将值 NULL 插入列 'sno'，表 'student.dbo.home'；列不允许有 Null 值。INSERT 失败。

description The server encountered an internal error that prevented it from fulfilling this request.

exception
org.apache.jasper.JasperException: javax.servlet.ServletException: com.microsoft.sqlserver.jdbc.SQLServerException: 不能将值 NULL 插入列 'sno'，表 'student.dbo.home'；列不允许有 Null 值。INSERT 失败。
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:560)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:461)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause
javax.servlet.ServletException: com.microsoft.sqlserver.jdbc.SQLServerException: 不能将值 NULL 插入列 'sno'，表 'student.dbo.home'；列不允许有 Null 值。INSERT 失败。
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:909)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:838)
org.apache.jsp.addhomesave_jsp._jspService(addhomesave_jsp.java:156)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause
com.microsoft.sqlserver.jdbc.SQLServerException: 不能将值 NULL 插入列 'sno'，表 'student.dbo.home'；列不允许有 Null 值。INSERT 失败。
com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(SQLServerException.java:217)
com.microsoft.sqlserver.jdbc.SQLServerStatement.getNextResult(SQLServerStatement.java:1635)
com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doExecutePreparedStatement(SQLServerPreparedStatement.java:426)
com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement$PrepStmtExecCmd.doExecute(SQLServerPreparedStatement.java:372)
com.microsoft.sqlserver.jdbc.TDSCommand.execute(IOBuffer.java:6276)
com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(SQLServerConnection.java:1794)
com.microsoft.sqlserver.jdbc.SQLServerStatement.executeCommand(SQLServerStatement.java:184)
com.microsoft.sqlserver.jdbc.SQLServerStatement.executeStatement(SQLServerStatement.java:159)
com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.executeUpdate(SQLServerPreparedStatement.java:315)
org.apache.jsp.addhomesave_jsp._jspService(addhomesave_jsp.java:132)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

note The full stack trace of the root cause is available in the Apache Tomcat/8.0.46 logs.
但sno是主键不能修改“允许NULL值”，也无法更改标识规范

Answer 1

sno字段设置了不能为空。
插入的时候，如果是NULL就会报错，需要给定一个非空值才行。