我的Kettle连不上sql server了，怎么解决？

我用kettle连接sql server，显示如下：
错误连接数据库 [Connect1] : org.pentaho.di.core.exception.KettleDatabaseException:
Error occurred while trying to connect to the database

Driver class 'net.sourceforge.jtds.jdbc.Driver' could not be found, make sure the 'MS SQL Server' driver (jar file) is installed.
net.sourceforge.jtds.jdbc.Driver


org.pentaho.di.core.exception.KettleDatabaseException:
Error occurred while trying to connect to the database

Driver class 'net.sourceforge.jtds.jdbc.Driver' could not be found, make sure the 'MS SQL Server' driver (jar file) is installed.
net.sourceforge.jtds.jdbc.Driver


at org.pentaho.di.core.database.Database.normalConnect(Database.java:472)
at org.pentaho.di.core.database.Database.connect(Database.java:370)
at org.pentaho.di.core.database.Database.connect(Database.java:341)
at org.pentaho.di.core.database.Database.connect(Database.java:331)
at org.pentaho.di.core.database.DatabaseFactory.getConnectionTestReport(DatabaseFactory.java:83)
at org.pentaho.di.core.database.DatabaseFactory.getConnectionTestResults(DatabaseFactory.java:112)
at org.pentaho.di.core.database.DatabaseMeta.testConnectionSuccess(DatabaseMeta.java:2811)
at org.pentaho.ui.database.event.DataHandler.testDatabaseConnection(DataHandler.java:621)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.pentaho.ui.xul.impl.AbstractXulDomContainer.invoke(AbstractXulDomContainer.java:313)
at org.pentaho.ui.xul.impl.AbstractXulComponent.invoke(AbstractXulComponent.java:157)
at org.pentaho.ui.xul.impl.AbstractXulComponent.invoke(AbstractXulComponent.java:141)
at org.pentaho.ui.xul.swt.tags.SwtButton.access$500(SwtButton.java:43)
at org.pentaho.ui.xul.swt.tags.SwtButton$4.widgetSelected(SwtButton.java:137)
at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Display.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
at org.eclipse.jface.window.Window.runEventLoop(Window.java:820)
at org.eclipse.jface.window.Window.open(Window.java:796)
at org.pentaho.di.ui.xul.KettleDialog.show(KettleDialog.java:80)
at org.pentaho.di.ui.xul.KettleDialog.show(KettleDialog.java:47)
at org.pentaho.di.ui.core.database.dialog.XulDatabaseDialog.open(XulDatabaseDialog.java:116)
at org.pentaho.di.ui.core.database.dialog.DatabaseDialog.open(DatabaseDialog.java:61)
at org.pentaho.di.ui.repo.controller.RepositoryConnectController.lambda$createConnection$1(RepositoryConnectController.java:129)
at org.eclipse.swt.widgets.RunnableLock.run(Unknown Source)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Unknown Source)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Unknown Source)
at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
at org.pentaho.di.ui.repo.dialog.RepositoryDialog.open(RepositoryDialog.java:95)
at org.pentaho.di.ui.repo.dialog.RepositoryDialog.open(RepositoryDialog.java:77)
at org.pentaho.di.ui.repo.dialog.RepositoryDialog.open(RepositoryDialog.java:73)
at org.pentaho.di.ui.repo.dialog.RepositoryDialog.openCreation(RepositoryDialog.java:109)
at org.pentaho.di.ui.repo.menu.RepositoryConnectMenu$1.widgetSelected(RepositoryConnectMenu.java:122)
at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Display.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
at org.pentaho.di.ui.spoon.Spoon.readAndDispatch(Spoon.java:1381)
at org.pentaho.di.ui.spoon.Spoon.waitForDispose(Spoon.java:7817)
at org.pentaho.di.ui.spoon.Spoon.start(Spoon.java:9179)
at org.pentaho.di.ui.spoon.Spoon.main(Spoon.java:707)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.pentaho.commons.launcher.Launcher.main(Launcher.java:92)
Caused by: org.pentaho.di.core.exception.KettleDatabaseException:
Driver class 'net.sourceforge.jtds.jdbc.Driver' could not be found, make sure the 'MS SQL Server' driver (jar file) is installed.
net.sourceforge.jtds.jdbc.Driver

at org.pentaho.di.core.database.Database.connectUsingClass(Database.java:515)
at org.pentaho.di.core.database.Database.normalConnect(Database.java:456)
... 53 more
Caused by: java.lang.ClassNotFoundException: net.sourceforge.jtds.jdbc.Driver
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
at org.pentaho.di.core.database.Database.connectUsingClass(Database.java:490)
... 54 more

主机名 : local
端口 : 1433
数据库名:AdventureWorksDW2012
请问大神该怎么处理？