Java can be used to generate .htpasswd files for Apache HTTP server authentication. This involves hashing passwords in a way that is compatible with Apache's authentication mechanism. Below, we use Java's cryptographic libraries for this purpose.

Ensure you have the Apache Commons Codec library available in your project for encoding the hashed password:

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.15</version>
</dependency>
            

Here's a simple Java method to create a new .htpasswd file:

import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.MessageDigest;
import org.apache.commons.codec.binary.Base64;

public void createHtpasswdFile(String username, String password) throws Exception {
    MessageDigest digest = MessageDigest.getInstance("SHA-256");
    byte[] hash = digest.digest(password.getBytes("UTF-8"));
    String encodedPassword = "{SHA}" + Base64.encodeBase64String(hash);

    String content = username + ":" + encodedPassword;
    Files.write(Paths.get(".htpasswd"), content.getBytes());
}
            

To add a new user to an existing .htpasswd file, append the user with a hashed password:

import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.security.MessageDigest;
import org.apache.commons.codec.binary.Base64;

public void appendUserToHtpasswdFile(String username, String password) throws Exception {
    MessageDigest digest = MessageDigest.getInstance("SHA-256");
    byte[] hash = digest.digest(password.getBytes("UTF-8"));
    String encodedPassword = "{SHA}" + Base64.encodeBase64String(hash);

    String content = "\n" + username + ":" + encodedPassword;
    Files.write(Paths.get(".htpasswd"), content.getBytes(), StandardOpenOption.APPEND);
}