IO流简单应用（文件加密和解密）

绝地灬酷狼 2022-07-14 14:34 174阅读 0赞

### 文件加密和解密 ###

package com.hz.test;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.io.RandomAccessFile;
    
    public class Test03 {
        
    
    static String filePath = "E:\\20160928JavaBase\\Test\\gg\\bbb111.txt";
    
        public static void main(String[] args) {
    
            /**
             * 文件加密
             */
            try {
                encrypt(filePath, "123456");
            } catch (IOException e) {
                e.printStackTrace();
            }
            /**
             * 文件解密
             */
    //      try {
        
    //          decrypt(filePath,"E:\\20160928JavaBase\\Test\\gg\\12345666.jpg",6);
    //      } catch (IOException e) {
        
    //          // TODO Auto-generated catch block
    //          e.printStackTrace();
    //      }
    //      readFileLastByte(filePath,6);
        }
        /**
         * 对文件进行file加密
         * @param fileUrl：文件路径
         * @param key：密码
         * @throws IOException
         */
    
        public static void encrypt(String fileUrl,String key) throws IOException {
    
            File file = new File(fileUrl);
            String path = file.getPath();
    
            if(!file.exists()){
                return;
            }
            int index = path.lastIndexOf("\\");
            System.out.println(index);
            String destFile = path.substring(0,index)+"\\"+"abc";
            System.out.println(destFile);
    
            File dest = new File(destFile);
            InputStream in = new FileInputStream(fileUrl);
            OutputStream out = new FileOutputStream(destFile);
    
            byte[] buffer = new byte[1024];
            byte[] buffer2 = new byte[1024];
            int r;
            while((r = in.read(buffer)) > 0){
                for (int i = 0; i < r; i++) {
                    byte b = buffer[i];
                    buffer2[i] = b == 255?0:++b;
                }
                out.write(buffer2,0,r);
                out.flush();
            }
            in.close();
            out.close();
            file.delete();
            dest.renameTo(new File(fileUrl));
            appendMethodA(fileUrl,key);
            System.out.println("加密成功");
    
        }
    
        /**
         * 
         * @param fileName
         * @param content 密匙
         */
        public static void appendMethodA(String fileName, String content) {
            try {
                //打开一个随机访问文件流，按读写方式
                RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");
                //文件长度，字节数
                long fileLength = randomFile.length();
                //将写文件指针移到文件尾
                randomFile.seek(fileLength);
                randomFile.writeBytes(content);
                randomFile.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
    
        }
    
    
        /**
         * 解密
         * @param fileUrl 源文件
         * @param tempUrl 临时文件
         * @param keyLength 密码长度
         * @throws IOException
         */
        public static String decrypt(String fileUrl,String tempUrl,int keyLength) throws IOException {
    
            File file = new File(fileUrl);
            if(!file.exists()){
                return null;
            }
            File dest = new File(tempUrl);
    
            if(!dest.getParentFile().exists()){
                dest.getParentFile().mkdirs();  
            }   
    
            InputStream is = new FileInputStream(fileUrl);
            OutputStream out = new FileOutputStream(tempUrl);
            byte[] buffer = new byte[1024];
            byte[] buffer2 = new byte[1024];
    
            byte bMax = (byte) 225;
            long size = file.length() - keyLength;
            int mod = (int) (size%1024);
            int div = (int) (size>>10);
            int count=mod == 0 ? div : (div+1);
    
            int k=1,r;
            while((k<=count && (r = is.read(buffer)) > 0)){
                if(mod != 0 && k==count){
                    r = mod;
                }
    
                for (int i = 0; i < r; i++) {
                    byte b = buffer[i];
                    buffer2[i]=b == 0 ? bMax : --b;
                }
    
                out.write(buffer2,0,r);
                k++;    
    
                out.close();
                is.close();
            }
            return tempUrl; 
        }
    }

### 在文件指定位置插入内容 ###

package com.hz.test;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.RandomAccessFile;
    
    public class InertContent {
        
    
        public static void main(String[] args) {
    
            try {
                Insert("E:\\20160928JavaBase\\Test01\\gg\\bbb.txt", 6, "你好好好");
            } catch (IOException e) {
    
                e.printStackTrace();
            }
        }
    
        public static void Insert(String fileName,long pos,String insertContent) throws IOException {
    
            RandomAccessFile raf = null;
            //创建一个临时文件来保存插入点后的数据
            File tmp = File.createTempFile("tmp", null);
            FileOutputStream tmpOut = null;
            FileInputStream tmpIn = null;
            tmp.deleteOnExit();
            try {
                raf = new RandomAccessFile(fileName,"rw");
                tmpOut = new FileOutputStream(tmp);
                tmpIn = new FileInputStream(tmp);
                raf.seek(pos);
                //将插入点后的内容读入临时文件中保存
                byte[] bbuf = new byte[63];
                //用于保存实际读取的字节数
                int hasRead = 0;
                while ((hasRead = raf.read(bbuf))>0) {
                    //将读取的数据写入临时文件
                    tmpOut.write(bbuf, 0, hasRead);
                }
                /*
                 * 插入
                 */
                //把文件记录指针重新定位到pos位置
                raf.seek(pos);
                //追加需要插入的内容
                raf.write(insertContent.getBytes());
                //追加临时文件的内容
                while((hasRead = tmpIn.read(bbuf)) > 0){
                    raf.write(bbuf, 0, hasRead);
                }
            } finally{
                raf.close();
            }
    
        }
    }