META-INF文件夹是干啥的,META-INF文件夹的作用, META-INF文件夹能删吗
今天有人问到 META-INF文件夹是干啥的,META-INF文件夹的作用, META-INF文件夹能删吗,还有项目的META-INF下面一般会有个MANIFEST.MF 文件,都是干啥的。
百度搜了一下,基本找不到答案。于是上stakoverflow搜,得到如下答案:
If you remove META-INF from a jar then there is no MANIFEST.MF and so java -jar can't find the main class.
You can create jars without META-INF but when you are going to execute a jar a META-INF/MANIFEST.MF is required.
See http://docs.oracle.com/javase/7/docs/technotes/guides/jar/jar.html
这句英文很简单,简单翻译如下:
如果你将Jar中的META-INF文件夹删除,那么jar文件里边就没有MANIFEST.MF文件。那么,java -jar就找不到main class.
没有META-INF你仍然可以创建一个Jar文件。但是,当你想要执行jar文件的时候,这个jar是需要具备 META-INF/MANIFEST.MF的。
我们在使用eclipse或者myeclipse新建项目之后,在项目中可以找到META-INF文件夹,下面有个MANIFEST.MF。
打开之后发现里边只有:
Manifest-Version: 1.0 Class-Path:
瞬间变有疑问:这么少点信息,有啥作用。为啥上面那段英文说的这个文件这么的不可或缺。
于是我随便在项目的lib中找了一个jar文件commons-io-2.3.jar,打开,把里边的MANIFEST.MF文件拿出来,打开如下:
Manifest-Version: 1.0 Export-Package: org.apache.commons.io.output;version="2.3",org.apache. commons.io.monitor;version="2.3",org.apache.commons.io.filefilter;ver sion="2.3",org.apache.commons.io.comparator;version="2.3",org.apache. commons.io.input;version="2.3",org.apache.commons.io;version="2.3" Implementation-Title: Commons IO Built-By: ggregory Tool: Bnd-1.50.0 Implementation-Vendor: The Apache Software Foundation Implementation-Vendor-Id: org.apache Specification-Title: Commons IO Bundle-License: http://www.apache.org/licenses/LICENSE-2.0.txt Bundle-SymbolicName: org.apache.commons.io X-Compile-Target-JDK: 1.6 Implementation-Version: 2.3 Specification-Vendor: The Apache Software Foundation Bundle-Name: Commons IO Created-By: Apache Maven Bundle Plugin X-Compile-Source-JDK: 1.6 Bundle-Vendor: The Apache Software Foundation Build-Jdk: 1.6.0_31 Bundle-Version: 2.3.0 Bnd-LastModified: 1334069963279 Bundle-ManifestVersion: 2 Bundle-Description: The Commons IO library contains utility classes, s tream implementations, file filters, file comparators, endian transfo rmation classes, and much more. Bundle-DocURL: http://commons.apache.org/io/ Implementation-Build: tags/2.3-RC1@r1311772; 2012-04-10 10:59:15-0400 Specification-Version: 2.3 Include-Resource: META-INF/LICENSE.txt=LICENSE.txt,META-INF/NOTICE.txt =NOTICE.txt Archiver-Version: Plexus Archiver
密密麻麻一大片,是一行行的,类似配置文件,前面一个'key' 后面一个‘value’
具体这些玩意有啥用,META-INF 里边还可以放啥,可击上面文字中提供的的连接。好长一片英文,感兴趣的话,慢慢看吧。
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