java中StringIndexOutOfBoundsException异常问题

在java中遇到StringIndexOutOfBoundsException异常问题：

• 如以下异常：

• `java.lang.reflect.InvocationTargetExceptionat 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:497)at com.csi.servlet.DispatcherServlet.service(DispatcherServlet.java:32)at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
  Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -1at java.lang.String.substring(String.java:1927)at com.csi.controller.UserInfoController.update(UserInfoController.java:370)... 25 more
  

• 这个问题就是字符串下标越界。

• 下面这个是出现异常的代码

• String realPath = request.getServletContext ().getRealPath ( "/front/upload" );File realDir = new File ( realPath );if (!realDir.exists ()) {realDir.mkdirs ();}String fileName = fileItem.getName ();String substring = fileName.substring ( fileName.lastIndexOf ( "." ) );IdWorker idWorker = new IdWorker ( 0 , 0 );String newName = idWorker.nextId () + substring;File uploadFile = new File ( realPath , newName );try {fileItem.write ( uploadFile );} catch (Exception e) {e.printStackTrace ();}userInfo.setUserHead ( "upload/" + newName );}
  

• 当：String fileName = fileItem.getName ();fileItem这个值是空值时执行这个语句：String substring = fileName.substring ( fileName.lastIndexOf ( “.” ) );就会抛出：java.lang.StringIndexOutOfBoundsException: String index out of range: -1这个异常，因为fileItem是空值substring ( fileName.lastIndexOf ( “.” ) )截取字符串语句执行失败就抛出异常。

解决方式：

•  if (fileItem.getName ().length ()>0) {String realPath = request.getServletContext ().getRealPath ( "/front/upload" );File realDir = new File ( realPath );if (!realDir.exists ()) {realDir.mkdirs ();}String fileName = fileItem.getName ();String substring = fileName.substring ( fileName.lastIndexOf ( "." ) );IdWorker idWorker = new IdWorker ( 0 , 0 );String newName = idWorker.nextId () + substring;File uploadFile = new File ( realPath , newName );try {fileItem.write ( uploadFile );} catch (Exception e) {e.printStackTrace ();}userInfo.setUserHead ( "upload/" + newName );}}
  

• 在上面添加判断语句：

• if (fileItem.getName ().length ()>0) {
  

• 如果传过来的的字符串长度大于0时才执行以下的语句，否则就跳过下面这些语句，防止下标越界，就是字符串为空时不能对字符串执行任何操作