Java#获取Jar包Version

场景

程序运行过程中，由于依赖传递导致类所在Jar包版本不正确时可使用。

代码一(spring-core)

获取Jar包里MANIFEST.MF中定义的Implementation-Version属性

package org.springframework.core;

/**
 * Fetches the "Implementation-Version" manifest attribute from the jar file.
 *
 * @author Juergen Hoeller
 * @since 1.1
 */
public final class SpringVersion {

	private SpringVersion() {
	}

	@Nullable
	public static String getVersion() {
		Package pkg = SpringVersion.class.getPackage();
		return (pkg != null ? pkg.getImplementationVersion() : null);
	}
}

Package类中VersionInfo类还包含其他信息

代码二(mybatisplus-core)

优先从Package中提取，提取不到再从CodeSource -> JarFile中提取

package com.baomidou.mybatisplus.core;

public class MybatisPlusVersion {

	public static String getVersion() {
        final Package pkg = MybatisPlusVersion.class.getPackage();
        if (pkg != null && pkg.getImplementationVersion() != null) {
            return pkg.getImplementationVersion();
        }
        CodeSource codeSource = MybatisPlusVersion.class.getProtectionDomain().getCodeSource();
        if (codeSource == null) {
            return null;
        }
        URL codeSourceLocation = codeSource.getLocation();
        try {
            URLConnection connection = codeSourceLocation.openConnection();
            if (connection instanceof JarURLConnection) {
                return getImplementationVersion(((JarURLConnection) connection).getJarFile());
            }
            try (JarFile jarFile = new JarFile(new File(codeSourceLocation.toURI()))) {
                return getImplementationVersion(jarFile);
            }
        } catch (Exception ex) {
            return null;
        }
    }

    private static String getImplementationVersion(JarFile jarFile) throws IOException {
        return jarFile.getManifest().getMainAttributes().getValue(Attributes.Name.IMPLEMENTATION_VERSION);
    }
}