java md5 sha256

╰+哭是因爲堅強的太久メ 2024-03-22 08:41 10阅读 0赞

### 省流 ###

String md5 = DigestUtils.md5Hex(inputStream);
    
    String md5 = DigestUtils.md5Hex(str);
    
    String md5 = DigestUtils.md5Hex(byteArray);

**这是commons-codec.jar**

[JAVA中获取文件MD5值的四种方法 - 腾讯云开发者社区-腾讯云 (tencent.com)][JAVA_MD5_ - _-_ _tencent.com]

一般上传文件，会用文件的md5作为文件名字，防止发生冲突。

guava:

> “ 如果必须与需要 MD5 的系统进行互操作，请使用此方法，尽管它已弃用。但是，如果您可以选择哈希函数，请避免使用 MD5，它既不快速也不安全。截至 2017 年 1 月，我们建议： 为了**安全起见：sha256** 或更高级别的 API。 **为了速度：使用 goodFastHash**  
> ”

[跟着 Guava 学 java 之 Hashing - 知乎 (zhihu.com)][Guava _ java _ Hashing - _ _zhihu.com]

[10-散列 | Google Guava 中文教程 (gitbooks.io)][10-_ _ Google Guava _ _gitbooks.io]

### guava 对文件hash ###

@Test
    public void givenFile_whenChecksumUsingGuava_thenVerifying() 
      throws IOException {
        String filename = "src/test/resources/test_md5.txt";
        String checksum = "5EB63BBBE01EEED093CB22BB8F5ACDC3";
            
        HashCode hash = com.google.common.io.Files
          .hash(new File(filename), Hashing.md5());
        String myChecksum = hash.toString().toUpperCase();
            
        assertThat(myChecksum.equals(checksum)).isTrue();
    }

[MD5 Hashing in Java | Baeldung][MD5 Hashing in Java _ Baeldung]

### guava md5 sha1 sha256 ###

import com.google.common.base.Charsets;
    import com.google.common.hash.Hashing;
    import org.junit.jupiter.api.Test;
    
    public class T1 {
     
         @Test
        public void GuavaHash(){
            String token = "123456789";
            //md5
            String md5 = Hashing.md5().newHasher().putString(token, Charsets.UTF_8).hash().toString();
            //sha1
            String sha1 = Hashing.sha1().newHasher().putString(token, Charsets.UTF_8).hash().toString();
            //sha256
            String sha256 = Hashing.sha256().newHasher().putString(token, Charsets.UTF_8).hash().toString();
    
            System.out.println(md5);//32个字符
            System.out.println(sha1);//40个字符
            System.out.println(sha256);//64个字符
        }
    }

### 源码 ###

public static String copyInputStreamToFileAndGetMd5Hex(InputStream inputStream, File file) throws IOException {
            FileUtils.copyInputStreamToFile(inputStream, file);
            return DigestUtils.md5Hex(new FileInputStream(file));
        }

DigestUtils源码，InputStream拆成长度1024的字节数组逐个MD5

public static MessageDigest updateDigest(final MessageDigest digest, final InputStream data) throws IOException {
            final byte[] buffer = new byte[STREAM_BUFFER_LENGTH];
            int read = data.read(buffer, 0, STREAM_BUFFER_LENGTH);
            while (read > -1) {
                digest.update(buffer, 0, read);
                read = data.read(buffer, 0, STREAM_BUFFER_LENGTH);
            }
            return digest;
        }

FileUtils.copyInputStreamToFile的源码，同样也是将InputStream拆成4096的字节数组，逐个写到目标文件中

public static long copyLarge(InputStream input, OutputStream output, byte[] buffer) throws IOException {
            long count;
            int n;
            for (count = 0L; -1 != (n = input.read(buffer)); count += (long) n) {
                output.write(buffer, 0, n);
            }
            return count;
        }

public static String copyInputStreamToFileAndGetMd5Hex(InputStream inputStream, File file) throws IOException {
            MessageDigest digest = DigestUtils.getMd5Digest();
            FileOutputStream outputStream = null;
            try {
                outputStream = new FileOutputStream(file);
                byte[] buffer = new byte[2048];
                int read = inputStream.read(buffer);
                while (read > -1) {
                    // 计算MD5,顺便写到文件
                    digest.update(buffer, 0, read);
                    outputStream.write(buffer, 0, read);
                    read = inputStream.read(buffer);
                }
            } finally {
                IOUtils.closeQuietly(outputStream);
            }
            return Hex.encodeHexString(digest.digest());
        }

[java计算md5 文件(File)、字符串(String)、输入流(InputStream)、资源(Resource)][java_md5 _File_String_InputStream_Resource]

hutool源码

public byte[] digest(InputStream data) {
            return this.digest(data, 8192);
        }

public byte[] digest(InputStream data, int bufferLength) throws IORuntimeException {
    
            byte[] result;
                if (ArrayUtil.isEmpty(this.salt)) {
                    result = this.digestWithoutSalt(data, bufferLength);
                } else {
                    result = this.digestWithSalt(data, bufferLength);
                }
            return this.resetAndRepeatDigest(result);
        }

循环读取InputStream，读取长度是8192，

private byte[] digestWithoutSalt(InputStream data, int bufferLength) throws IOException {
    		final byte[] buffer = new byte[bufferLength];
    		int read;
    		while ((read = data.read(buffer, 0, bufferLength)) > -1) {
    			this.digest.update(buffer, 0, read);
    		}
    		return this.digest.digest();
    	}

this.digest就是java.security.MessageDigest

[JAVA_MD5_ - _-_ _tencent.com]: https://cloud.tencent.com/developer/article/1854222
[Guava _ java _ Hashing - _ _zhihu.com]: https://zhuanlan.zhihu.com/p/598768766
[10-_ _ Google Guava _ _gitbooks.io]: https://wizardforcel.gitbooks.io/guava-tutorial/content/26.html
[MD5 Hashing in Java _ Baeldung]: https://www.baeldung.com/java-md5
[java_md5 _File_String_InputStream_Resource]: https://blog.csdn.net/abcdu1/article/details/117964992