获取文件的md5(java & php)
每个文件都可以用MD5验证程序算出一个固定的md5码来,它是一个文件的文件签名,可用于验证自己下载的软件是否为原版。百度网盘的“秒传”应该也用到了这个,即上传之前首先计算该文件的md5,然后看服务器上有没有该文件,有的话从服务端直接拷贝,节省上传时
每个文件都可以用MD5验证程序算出一个固定的md5码来,它是一个文件的文件签名,可用于验证自己下载的软件是否为原版。百度网盘的“秒传”应该也用到了这个,即上传之前首先计算该文件的md5值,然后看服务器上有没有该文件,有的话从服务端直接拷贝,节省上传时间和降低网络负担。
java的MD5util类:
import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class MD5FileUtil { private static final Logger logger = LoggerFactory .getLogger(MD5FileUtil.class); protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; protected static MessageDigest messagedigest = null; static { try { messagedigest = MessageDigest.getInstance("MD5"); } catch (NoSuchAlgorithmException e) { logger.error("MD5FileUtil messagedigest初始化失败", e); } } public static String getFileMD5String(File file) throws IOException { FileInputStream in = new FileInputStream(file); FileChannel ch = in.getChannel(); MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length()); messagedigest.update(byteBuffer); return bufferToHex(messagedigest.digest()); } public static String getMD5String(String s) { return getMD5String(s.getBytes()); } public static String getMD5String(byte[] bytes) { messagedigest.update(bytes); return bufferToHex(messagedigest.digest()); } private static String bufferToHex(byte bytes[]) { return bufferToHex(bytes, 0, bytes.length); } private static String bufferToHex(byte bytes[], int m, int n) { StringBuffer stringbuffer = new StringBuffer(2 * n); int k = m + n; for (int l = m; l > 4]; char c1 = hexDigits[bt & 0xf]; stringbuffer.append(c0); stringbuffer.append(c1); } public static boolean checkPassword(String password, String md5PwdStr) { String s = getMD5String(password); return s.equals(md5PwdStr); } public static void main(String[] args) throws IOException { long begin = System.currentTimeMillis(); File big = new File("D:\\temp\\jre-7u11-linux-i586.tar.gz"); String md5 = getFileMD5String(big); long end = System.currentTimeMillis(); System.out.println("md5:" + md5); System.out.println("time:" + ((end - begin) / 1000) + "s"); } }
php
例子1:
<?php $filename = "test.txt"; $md5file = md5_file($filename); echo $md5file; ?>
会输出类似下面一串字符:
5d41402abc4b2a76b9719d911017c592
<?php $md5file = md5_file("test.txt"); file_put_contents("md5file.txt",$md5file); ?>
//在本例中,我们将检测 "test.txt" 是否已被更改(即是否 MD5 散列已被更改):
<?php $md5file = file_get_contents("md5file.txt"); if (md5_file("test.txt") == $md5file) { echo "The file is ok."; } else { echo "The file has been changed."; } ?>
输出:
The file is ok.

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.

PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7

PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.

In PHP8, match expressions are a new control structure that returns different results based on the value of the expression. 1) It is similar to a switch statement, but returns a value instead of an execution statement block. 2) The match expression is strictly compared (===), which improves security. 3) It avoids possible break omissions in switch statements and enhances the simplicity and readability of the code.

In PHP, you can effectively prevent CSRF attacks by using unpredictable tokens. Specific methods include: 1. Generate and embed CSRF tokens in the form; 2. Verify the validity of the token when processing the request.
