java中StringIndexOutOfBoundsException异常问题

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IT枫斗者 2024-05-09 17:33:21 博主文章分类：java错误分析 ©著作权

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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.InvocationTargetException
	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: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: -1
	at 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 );
                }
            }