如何配置maven-assembly-plugin调整tar.xz包内文件顺序以优化压缩率

Great question! The maven-assembly-plugin doesn't have built-in support for reordering files in the generated archive to group identical content together for better xz compression. But we can work around this by splitting the process into two steps: first generate an uncompressed tar archive, then reorder its contents by file content (to group duplicates) and recompress it into txz. Here's how to implement this:

Step 1: Adjust the Maven Assembly Plugin to Output an Uncompressed Tar #

First, modify your pom.xml to have the assembly plugin generate a raw tar file instead of txz—we'll handle compression later after reordering:

<build>
  <plugins>
    <!-- Modified assembly plugin: output tar instead of txz -->
    <plugin>
      <artifactId>maven-assembly-plugin</artifactId>
      <version>3.1.1</version>
      <executions>
        <execution>
          <phase>package</phase>
          <goals>
            <goal>single</goal>
          </goals>
          <configuration>
            <finalName>myapp</finalName>
            <descriptors>
              <descriptor>delivery/assembly/distribute-install.xml</descriptor>
            </descriptors>
            <!-- Switch format from txz to tar -->
            <formats>
              <format>tar</format>
            </formats>
          </configuration>
        </execution>
      </executions>
    </plugin>

    <!-- Add plugin to copy and set permissions on our reorder script -->
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-resources-plugin</artifactId>
      <version>3.3.1</version>
      <executions>
        <execution>
          <id>copy-scripts</id>
          <phase>prepare-package</phase>
          <goals>
            <goal>copy-resources</goal>
          </goals>
          <configuration>
            <outputDirectory>${project.build.directory}</outputDirectory>
            <resources>
              <resource>
                <directory>src/main/scripts</directory>
                <includes>
                  <include>reorder-tar.sh</include>
                </includes>
                <fileMode>0755</fileMode> <!-- Make script executable -->
              </resource>
            </resources>
          </configuration>
        </execution>
      </executions>
    </plugin>

    <!-- Add exec plugin to run the reordering script -->
    <plugin>
      <groupId>org.codehaus.mojo</groupId>
      <artifactId>exec-maven-plugin</artifactId>
      <version>3.1.0</version>
      <executions>
        <execution>
          <phase>package</phase>
          <goals>
            <goal>exec</goal>
          </goals>
          <configuration>
            <executable>bash</executable>
            <arguments>
              <argument>${project.build.directory}/reorder-tar.sh</argument>
              <argument>${project.build.directory}/myapp.tar</argument>
              <argument>${project.build.directory}/myapp.txz</argument>
            </arguments>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

Step 2: Create the Reordering Script #

Create a shell script src/main/scripts/reorder-tar.sh that will:

1. Extract the raw tar to a temporary directory
2. Sort files by their content hash (to group identical files together)
3. Recreate the tar with sorted files and compress it to txz

#!/bin/bash
INPUT_TAR="$1"
OUTPUT_TXZ="$2"
TMP_DIR=$(mktemp -d)

# Extract the original tar to a temp workspace
tar -xf "$INPUT_TAR" -C "$TMP_DIR"

# Navigate to the temp dir and generate a sorted file list by content MD5
cd "$TMP_DIR"
sorted_files=$(find . -type f | while read file; do
  echo "$(md5sum "$file") $file"
done | sort | cut -d' ' -f3-)

# Re-pack the sorted files into a new tar, then compress with high-rate xz
tar -cf - $sorted_files | xz -9 > "$OUTPUT_TXZ"

# Cleanup temporary files and original tar
rm -rf "$TMP_DIR"
rm "$INPUT_TAR"

How This Works #

• By sorting files by their MD5 hash, identical files (even in different paths) will be grouped consecutively in the new tar archive.
• XZ compression excels at compressing repeated content, so this grouping will drastically reduce the final archive size by eliminating redundant compressed data.

Windows Environment Note #

If you're working on Windows, replace the bash script with a PowerShell equivalent. The core logic remains the same: extract, sort by file hash, re-pack, and compress.

内容的提问来源于stack exchange，提问作者TomTom