如何在java中将两个不同的excel文件作为数据库连接到同一台服务器上？
我使用两个不同的连接变量con1和con2连接了两个excel数据库。我希望通过匹配两个数据库中的列，从第二个数据库中检索数据。我如何在java中做到这一点？我已经试了很多次了。当我运行这段代码时，我得到了NullPointerException
try
{
sql10 = "select [Data$].Species,[Plot$].District,[Plot$].State from [Plot$],[Data$] where [Data$].Plot_ID = ? ";
pst10=con.prepareStatement(sql10);
pst10.setString(1, tmp1);
rs14=pst10.executeQuery();
while(rs14.next())
{
String st=rs14.getString("State");
String dis=rs14.getString("District");
String sp=rs14.getString("Species");
System.out.println(sp);
sql11="select * from [database$] where State = st and District = dis and Species = sp";
pst11=con1.prepareStatement(sql11);
pst11.setString(1, tmp1);
rs15=pst11.executeQuery();
while(rs15.next())
{
System.out.println(rs15.getString("Local_equation"));
}
}
堆栈跟踪是：
java.lang.NullPointerException
at sun.jdbc.odbc.JdbcOdbcPreparedStatement.clearParameter(JdbcOdbcPreparedStatement.java:1022)
at sun.jdbc.odbc.JdbcOdbcPreparedStatement.setChar(JdbcOdbcPreparedStatement.java:3056)
at sun.jdbc.odbc.JdbcOdbcPreparedStatement.setString(JdbcOdbcPreparedStatement.java:765)
at biomasscal.GLA14.buttonCALCULATEActionPerformed(GLA14.java:599)
at biomasscal.GLA14.access$400(GLA14.java:60)
at biomasscal.GLA14$5.actionPerformed(GLA14.java:279)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6504)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6269)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4860)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4686)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2713)
at java.awt.Component.dispatchEvent(Component.java:4686)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:680)
at java.awt.EventQueue$4.run(EventQueue.java:678)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
# 1 楼答案
在查询第二个excel数据库时，需要将第一次查询中的变量作为参数传入（如前所述）：
然而，由于没有看到完整的堆栈跟踪，我无法确定