blocks|key|1193141|text|以下是Java查找此信息的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193142|Windows：javap+-v+<class>+%7C+findstr+major|offset|length|style|CODE|1193143|Unix：javap+-v+<class>+%7C+grep+major|1193144|例如：|1193145|>+javap+-v+Application+%7C+findstr+major+  major+version:+51|1193146|entityMap^0|0|8|W|0|5|T|0|0|0|1M|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@$D|R|E|S|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|W|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|X|8|@$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|N|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|O|$]]

Here is Java's way to find this information.

Windows: <code>javap -v &lt;class&gt; | findstr major</code> 
Unix: <code>javap -v &lt;class&gt; | grep major</code>


For example: 
<code>&gt; javap -v Application | findstr major
&nbsp;&nbsp;major version: 51
</code>

blocks|key|1193415|text|不需要解压JAR+(如果其中一个类名已知或使用7zip查找)，因此在Windows上，以下内容就足够了：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193416|javap+-cp+log4j-core-2.5.jar+-verbose+org.apache.logging.log4j.core.Logger+%7C+findstr+major|code-block|syntax|javascript|1193417|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

There is no need to unpack the JAR (if one of the class names is known or is looked up e.g. using 7zip), so on Windows the following would be sufficient:

<pre><code>javap -cp log4j-core-2.5.jar -verbose org.apache.logging.log4j.core.Logger | findstr major
</code></pre>

blocks|key|978742|text|Java编译器(javac)不构建jars，它将Java文件转换为类文件。Jar工具(jar)创建实际的Jar。如果未指定自定义清单，则默认清单将指定使用哪个版本的JDK来创建jar。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|978743|entityMap^0|8|5|17|3|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

The Java compiler (<code>javac</code>) does not build jars, it translates Java files into class files. The Jar tool (<code>jar</code>) creates the actual jars. If no custom manifest was specified, the default manifest will specify which version of the JDK was used to create the jar.

blocks|key|1193642|text|您可以使用十六进制编辑器从.class文件中查找Java编译器版本。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193643|步骤1:使用压缩包从jar文件中提取.class文件|1193644|第二步:用十六进制编辑器打开.class文件。(我用过notepad%2B%2B十六进制编辑器插件。这个插件以二进制格式读取文件，并以十六进制显示)你可以在下面看到。|1193645|📷|atomic|offset|length|1193646|​|1193647|索引6和7给出了正在使用的类文件格式的主版本号。https://en.wikipedia.org/wiki/Java_class_file|1193648|Java+SE+11+=+55+(十六进制0x37)|1193649|Java+SE+10+=+54+(十六进制0x36)|1193650|Java+SE+9=+53+(十六进制0x35)|1193651|Java+SE+8=+52+(0x34十六进制)，|1193652|Java+SE+7=+51+(0x33十六进制)，|1193653|Java+SE+6.0+=+50+(0x32十六进制)，|1193654|Java+SE+5.0+=+49+(0x31十六进制)，|1193655|JDK+1.4+=+48+(0x30十六进制)，|1193656|JDK+1.3+=+47+(0x2F十六进制)，|1193657|JDK+1.2+=+46+(0x2E十六进制)，|1193658|JDK+1.1+=+45+(0x2D十六进制)。|1193659|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/06472fae29a77c2ee102d15850413854.png|imageAlt|1|LINK|MUTABLE|url|https://en.wikipedia.org/wiki/Java_class_file^0|0|0|0|0|1|0|0|0|O|19|1|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|1R|8|@]|9|@$I|1S|J|1T|1|1U]]|A|$]]|$1|K|3|L|5|6|7|1V|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1W|8|@]|9|@$I|1X|J|1Y|1|1Z]]|A|$]]|$1|O|3|P|5|6|7|20|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|21|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|22|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|23|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|24|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|25|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|26|8|@]|9|@]|A|$]]|$1|12|3|13|5|6|7|27|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|28|8|@]|9|@]|A|$]]|$1|16|3|17|5|6|7|29|8|@]|9|@]|A|$]]|$1|18|3|19|5|6|7|2A|8|@]|9|@]|A|$]]|$1|1A|3|-4|5|6|7|2B|8|@]|9|@]|A|$]]]|1B|$1C|$5|1D|1E|1F|A|$1G|1H|1I|-4]]|1J|$5|1K|1E|1L|A|$1M|1N]]]]

you can find Java compiler version from .class files using a Hex Editor.

Step 1:
Extract .class files from jar file using a zip extractor

step 2: open .class file with a hex editor.(I have used notepad++ hex editor plugin. This plugin reads file as binary and shows it in hex)
You can see below. 
<a href="https://i.stack.imgur.com/e5c3H.png" rel="noreferrer"><img src="https://i.stack.imgur.com/e5c3H.png" alt="enter image description here"></a>

Index 6 and 7 gives major version number of the class file format being used.
<a href="https://en.wikipedia.org/wiki/Java_class_file" rel="noreferrer">https://en.wikipedia.org/wiki/Java_class_file</a>

Java SE 11 = 55 (0x37 hex)

Java SE 10 = 54 (0x36 hex)

Java SE 9 = 53 (0x35 hex)

Java SE 8 = 52 (0x34 hex),

Java SE 7 = 51 (0x33 hex),

Java SE 6.0 = 50 (0x32 hex),

Java SE 5.0 = 49 (0x31 hex),

JDK 1.4 = 48 (0x30 hex),

JDK 1.3 = 47 (0x2F hex),

JDK 1.2 = 46 (0x2E hex),

JDK 1.1 = 45 (0x2D hex).

blocks|key|1192919|text|您可以通过inspecting+the+first+8+bytes+(或者使用可以这样做的app+)来判断Java二进制版本。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1192920|据我所知，编译器本身不会插入任何标识签名。无论如何，我在VM+spec+class+format文件中找不到这样的东西。|1192921|entityMap|0|LINK|mutability|MUTABLE|url|http://illegalargumentexception.blogspot.com/2009/07/java-finding-class-versions.html|1|http://illegalargumentexception.blogspot.com/2009/11/java-application-to-check-binary-class.html|2|http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html^0|5|S|0|19|3|1|0|S|K|2|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]|$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|F|3|-4|5|6|7|12|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]|P|$5|I|J|K|C|$L|Q]]]]

You can tell the Java binary version by <a href="http://illegalargumentexception.blogspot.com/2009/07/java-finding-class-versions.html" rel="nofollow noreferrer">inspecting the first 8 bytes</a> (or using an <a href="http://illegalargumentexception.blogspot.com/2009/11/java-application-to-check-binary-class.html" rel="nofollow noreferrer">app</a> that can).

The compiler itself doesn't, to the best of my knowledge, insert any identifying signature. I can't spot such a thing in the file <a href="http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html" rel="nofollow noreferrer">VM spec class format</a> anyway.

blocks|key|978865|text|code+posted+by+Owen可以告诉您这里的许多其他答案提到的信息：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|978866|public+void+simpleExample+()
{
++++FileInputStream+fis+=+new+FileInputStream+("mytest.class");
++++parseJavaClassFile+(+fis+);
}
protected+void+parseJavaClassFile+(+InputStream+classByteStream+)+throws+Exception
{
++++DataInputStream+dataInputStream+=+new+DataInputStream+(+classByteStream+);
++++magicNumber+=+dataInputStream.readInt();
++++if+(+magicNumber+==+0xCAFEBABE+)
++++{
++++++++int+minorVer+=+dataInputStream.readUnsignedShort();
++++++++int+majorVer+=+dataInputStream.readUnsignedShort();
++++++++//+do+something+here+with+major+&+minor+numbers
++++}
}|code-block|syntax|javascript|978867|另请参阅this和this站点。我最终快速修改了Mind+Products代码，以检查我的每个依赖项是为什么而编译的。|978868|entityMap|0|LINK|mutability|MUTABLE|url|http://www.thatsjava.com/java-essentials/30681/|1|http://mindprod.com/products1.html#JARCHECK|2|http://clirr.sourceforge.net/^0|0|J|0|0|0|4|4|1|9|4|2|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]|$A|15|B|16|1|17]]|C|$]]|$1|K|3|-4|5|6|7|18|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]|U|$5|N|O|P|C|$Q|V]]]]

The <a href="http://www.thatsjava.com/java-essentials/30681/" rel="nofollow noreferrer">code posted by Owen</a> can tell you the information mentioned by a number of the other answers here:

<pre><code>public void simpleExample ()
{
 FileInputStream fis = new FileInputStream ("mytest.class");
 parseJavaClassFile ( fis );
}
protected void parseJavaClassFile ( InputStream classByteStream ) throws Exception
{
 DataInputStream dataInputStream = new DataInputStream ( classByteStream );
 magicNumber = dataInputStream.readInt();
 if ( magicNumber == 0xCAFEBABE )
 {
 int minorVer = dataInputStream.readUnsignedShort();
 int majorVer = dataInputStream.readUnsignedShort();
 // do something here with major &amp; minor numbers
 }
}
</code></pre>

See also <a href="http://mindprod.com/products1.html#JARCHECK" rel="nofollow noreferrer">this</a> and <a href="http://clirr.sourceforge.net/" rel="nofollow noreferrer">this</a> site. I ended up modifying the Mind Products code quickly to check what each of my dependencies was compiled for.

blocks|key|1193237|text|One+liner+(Linux)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193238|unzip+-p+mylib.jar+META-INF/MANIFEST.MF|offset|length|style|CODE|1193239|这会将MANIFEST.MF文件的内容打印到标准输出(希望jar文件中有这样的内容:)|1193240|根据构建包的内容，您可以在Created-By或Build-Jdk密钥中找到JDK版本。|1193241|entityMap^0|0|0|13|0|3|B|0|D|A|O|9|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@$D|P|E|Q|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|R|8|@$D|S|E|T|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|U|8|@$D|V|E|W|F|G]|$D|X|E|Y|F|G]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|M|$]]

One liner (Linux)

<code>unzip -p mylib.jar META-INF/MANIFEST.MF</code>

This prints the content of <code>MANIFEST.MF</code> file to stdout (hopefully there is one in your jar file :)

Depending on what built your package, you will find the JDK version in <code>Created-By</code> or <code>Build-Jdk</code> key.

blocks|key|1193050|text|每个类文件都嵌入了字节码级别的版本号，JVM使用该版本号查看它是否喜欢特定的字节码块。对于Java+1.4是48，对于Java+1.5是49，对于Java+6是50。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193051|有许多编译器可以在每个级别生成字节码，javac使用"-target“选项来指示要生成哪个字节码级别，Java6javac可以生成至少1.4、1.5和6的字节码。我不相信编译器会插入任何可以识别编译器本身的东西，而这正是我认为您所要求的。Eclipse编译器也越来越多地被使用，因为它是一个单独的jar，只能与JRE一起运行。|1193052|在jar文件中，通常有许多类，并且每个类都是独立的，因此您需要调查jar中的所有类，以确定内容的特征。|1193053|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Each class file has a version number embedded for the byte code level which the JVM use to see if it likes that particular byte code chunk or not. This is 48 for Java 1.4, 49 for Java 1.5 and 50 for Java 6.

Many compilers exist which can generate byte code at each level, javac uses the "-target" option to indicate which byte code level to generate, and the Java 6 javac can generate byte code for at least 1.4, 1.5 and 6. I do not believe that the compiler inserts anything that can identify the compiler itself which is what I think you ask for. Also the Eclipse compiler is increasingly being used, as it is a single jar which can run with the JRE only.

In a jar file there is usually many classes, and each of them is independent, so you need to investigate all classes in the jar to be certain about the characteristics of the contents.

blocks|key|1193362|text|很多时候，您可能会看到整个jar文件，或者除了自身之外还包含许多jar文件的war文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193363|因为我不想手动检查每个类，所以我编写了一个java程序来做这件事：|1193364|https://github.com/Nthalk/WhatJDK|offset|length|1193365|./whatjdk+some.war
some.war:WEB-INF/lib/xml-apis-1.4.01.jar+contains+classes+compatible+with+Java1.1
some.war+contains+classes+compatible+with+Java1.6|code-block|syntax|javascript|1193366|虽然这并没有说明类是用什么编译的，但它决定了哪些JDK将能够加载类，这可能是您一开始想要的。|1193367|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|X|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@$F|Y|G|Z|1|10]]|A|$]]|$1|H|3|I|5|J|7|11|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|12|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|E]]]]

A good deal of times, you might be looking at whole jar files, or war files that contain many jar files in addition to themselves.

Because I didn't want to hand check each class, I wrote a java program to do that:

<a href="https://github.com/Nthalk/WhatJDK" rel="nofollow">https://github.com/Nthalk/WhatJDK</a>

<pre><code>./whatjdk some.war
some.war:WEB-INF/lib/xml-apis-1.4.01.jar contains classes compatible with Java1.1
some.war contains classes compatible with Java1.6
</code></pre>

While this doesn't say what the class was compiled WITH, it determines what JDK's will be able to LOAD the classes, which is probably what you wanted to begin with.

blocks|key|1193096|text|根据@David+J.Liszewski的回答，我运行以下命令在Ubuntu上提取jar文件的清单：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193097|#+Determine+the+manifest+file+name:
$+jar+tf+LuceneSearch.jar+%7C+grep+-i+manifest
META-INF/MANIFEST.MF

#+Extract+the+file:
$+sudo+jar+xf+LuceneSearch.jar+META-INF/MANIFEST.MF

#+Print+the+file's+contents:
$+more+META-INF/MANIFEST.MF
Manifest-Version:+1.0
Ant-Version:+Apache+Ant+1.8.2
Created-By:+1.7.0_25-b30+(Oracle+Corporation)
Main-Class:+org.wikimedia.lsearch.config.StartupManager|code-block|syntax|javascript|1193098|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Following up on @David J. Liszewski's answer, I ran the following commands to extract the jar file's manifest on Ubuntu:

<pre><code># Determine the manifest file name:
$ jar tf LuceneSearch.jar | grep -i manifest
META-INF/MANIFEST.MF

# Extract the file:
$ sudo jar xf LuceneSearch.jar META-INF/MANIFEST.MF

# Print the file's contents:
$ more META-INF/MANIFEST.MF
Manifest-Version: 1.0
Ant-Version: Apache Ant 1.8.2
Created-By: 1.7.0_25-b30 (Oracle Corporation)
Main-Class: org.wikimedia.lsearch.config.StartupManager
</code></pre>

blocks|key|979335|text|我还编写了自己的bash脚本来转储命令行传递的所有jars所需的Java版本……我的有点粗糙，但对我来说很有效;-)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|979336|示例用法|979337|$+jar_dump_version_of_jvm_required.sh+*.jar
JVM+VERSION+REQUIRED:+46.0,+/private/tmp/jars/WEB-INF/lib/json-simple-1.1.jar
JVM+VERSION+REQUIRED:+49.0,+/private/tmp/jars/WEB-INF/lib/json-smart-1.1.1.jar
JVM+VERSION+REQUIRED:+50.0,+/private/tmp/jars/WEB-INF/lib/jsontoken-1.0.jar
JVM+VERSION+REQUIRED:+50.0,+/private/tmp/jars/WEB-INF/lib/jsr166y-1.7.0.jar|code-block|syntax|javascript|979338|jar_dump_version_of_jvm_required.sh|979339|#!/bin/bash

DIR=$(PWD)
function+show_help()
{
++ME=$(basename+$0)
++IT=$(cat+<<EOF

++Dumps+the+version+of+the+JVM+required+to+run+the+classes+in+a+jar+file

++usage:+$ME+JAR_FILE

++e.g.+

++$ME+myFile.jar++++->++VERSION:+50.0+++++myFile.jar

++Java+versions+are:
++54+=+Java+10
++53+=+Java+9
++52+=+Java+8
++51+=+Java+7
++50+=+Java+6
++49+=+Java+5
++48+=+Java+1.4
++47+=+Java+1.3
++46+=+Java+1.2
++45.3+=+Java+1.1

EOF
++)
++echo+"$IT"
++exit
}

if+[+"$1"+==+"help"+]
then
++show_help
fi
if+[+-z+"$1"+]
then
++show_help
fi

function+unzipJarToTmp()
{
++JAR=$1
++CLASS_FILE=$(jar+-tf+"$JAR"+%7C+grep+\.class$+%7C+grep+-v+'\$'+%7C+head+-n1+%7C+awk+'{print+$NF}')
++OUT_FILE="$CLASS_FILE"
++#echo+"J=$JAR+C=$CLASS_FILE+O=$OUT_FILE"
++jar+xf+"$JAR"+"$CLASS_FILE"

++MAJOR=$(javap+-v+"$OUT_FILE"+2>&1+%7C+grep+major+%7C+awk+-F'+'+'{print+$3'})
++MINOR=$(javap+-v+"$OUT_FILE"+2>&1+%7C+grep+minor+%7C+awk+-F'+'+'{print+$3'})
++if+[+-z+"$MAJOR"+]
++then
++++echo+"JVM+VERSION+REQUIRED:+NA+as+no+classes+in+$JAR"
++else
++++echo+"JVM+VERSION+REQUIRED:+$MAJOR.$MINOR,+$JAR"
++fi
}

#+loop+over+cmd+line+args
for+JAR+in+"$@"
do
++cd+"$DIR"
++JAR_UID=$(basename+"$JAR"+%7C+sed+s/.jar//g)
++TMPDIR=/tmp/jar_dump/$JAR_UID/
++mkdir+-p+"$TMPDIR"
++JAR_ABS_PATH=$(realpath+$JAR)

++cd+"$TMPDIR"

++#echo+"$JAR_ABS_PATH"
++unzipJarToTmp+"$JAR_ABS_PATH"
++#sleep+2
done|979340|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I as well wrote my own bash script to dump the Java version required by all the jars passed at the command line... Mine is a bit rough, but works for me ;-)

<h3>example usage</h3>

<pre><code>$ jar_dump_version_of_jvm_required.sh *.jar
JVM VERSION REQUIRED: 46.0, /private/tmp/jars/WEB-INF/lib/json-simple-1.1.jar
JVM VERSION REQUIRED: 49.0, /private/tmp/jars/WEB-INF/lib/json-smart-1.1.1.jar
JVM VERSION REQUIRED: 50.0, /private/tmp/jars/WEB-INF/lib/jsontoken-1.0.jar
JVM VERSION REQUIRED: 50.0, /private/tmp/jars/WEB-INF/lib/jsr166y-1.7.0.jar
</code></pre>

<h3>jar_dump_version_of_jvm_required.sh</h3>

<pre><code>#!/bin/bash

DIR=$(PWD)
function show_help()
{
 ME=$(basename $0)
 IT=$(cat &lt;&lt;EOF

 Dumps the version of the JVM required to run the classes in a jar file

 usage: $ME JAR_FILE

 e.g. 

 $ME myFile.jar -&gt; VERSION: 50.0 myFile.jar

 Java versions are:
 54 = Java 10
 53 = Java 9
 52 = Java 8
 51 = Java 7
 50 = Java 6
 49 = Java 5
 48 = Java 1.4
 47 = Java 1.3
 46 = Java 1.2
 45.3 = Java 1.1

EOF
 )
 echo "$IT"
 exit
}

if [ "$1" == "help" ]
then
 show_help
fi
if [ -z "$1" ]
then
 show_help
fi

function unzipJarToTmp()
{
 JAR=$1
 CLASS_FILE=$(jar -tf "$JAR" | grep \.class$ | grep -v '\$' | head -n1 | awk '{print $NF}')
 OUT_FILE="$CLASS_FILE"
 #echo "J=$JAR C=$CLASS_FILE O=$OUT_FILE"
 jar xf "$JAR" "$CLASS_FILE"

 MAJOR=$(javap -v "$OUT_FILE" 2&gt;&amp;1 | grep major | awk -F' ' '{print $3'})
 MINOR=$(javap -v "$OUT_FILE" 2&gt;&amp;1 | grep minor | awk -F' ' '{print $3'})
 if [ -z "$MAJOR" ]
 then
 echo "JVM VERSION REQUIRED: NA as no classes in $JAR"
 else
 echo "JVM VERSION REQUIRED: $MAJOR.$MINOR, $JAR"
 fi
}

# loop over cmd line args
for JAR in "$@"
do
 cd "$DIR"
 JAR_UID=$(basename "$JAR" | sed s/.jar//g)
 TMPDIR=/tmp/jar_dump/$JAR_UID/
 mkdir -p "$TMPDIR"
 JAR_ABS_PATH=$(realpath $JAR)

 cd "$TMPDIR"

 #echo "$JAR_ABS_PATH"
 unzipJarToTmp "$JAR_ABS_PATH"
 #sleep 2
done
</code></pre>

blocks|key|1193491|text|签入jar示例的Manifest文件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1193492|清单-版本:+1.0创建者:+1.6.0+(IBM+Corporation)|1193493|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You check in Manifest file of jar
example:

Manifest-Version: 1.0
Created-By: 1.6.0 (IBM Corporation)

blocks|key|1193205|text|我使用file命令根据Davids的建议构建了一个小的bash脚本(on+github)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1193206|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/beardedN5rd/java-helper/blob/master/scripts/checkJavaVersion.sh^0|3|4|X|B|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

I build a little bash script <a href="https://github.com/beardedN5rd/java-helper/blob/master/scripts/checkJavaVersion.sh" rel="nofollow">(on github)</a> based on Davids suggestion using the <code>file</code> command

How can I tell what version of the Java compiler was used to build a jar? I have a jar file, and it could have been built in any one of three JDKs. We need to know exactly which one, so we can certify compatibility. Is the compiler version embedded somewhere in the class files or jar?

What version of javac built my jar?

编译器

Windows

Eclipse

Ubuntu

Linux

Java

Unix

如何知道构建jar使用的是哪个版本的Java编译器？我有一个jar文件，它可以构建在三个JDK中的任何一个中。我们需要确切地知道是哪一个，这样我们才能证明兼容性。编译器版本是否嵌入在类文件或jar中的某个位置？

问哪个版本的javac构建了我的jar？
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