修改jar源码

客官°小女子只卖身不卖艺 2022-05-25 03:42 327阅读 0赞

我所使用的步骤:  
1.如想要修改java.lang.Object源码;新建Object.java,package 路径为package java.lang; ;  
2.使用反编译工具,将想要修改的源文件比如Object.class打开,copy其内容到1的java文件中;  
3.使用java编译命令(这算是比较低级的做法)编译Object.java为Object.class文件;(也可以利用eclipse的编译功能.)  
4.使用压缩软件打开(而不是解压,如果解压的话还要再麻烦一些)rt.jar,替换其下的/lang/Object.class文件  
5.测试.

其中出现的问题有:  
1.  
![这里写图片描述][70]

java版本有问题:

Java SE 10 = 54, Java SE 9 = 53, Java SE 8 = 52, Java SE 7 = 51, Java SE 6.0 = 50, Java SE 5.0 = 49, JDK 1.4 = 48, JDK 1.3 = 47, JDK 1.2 = 46, JDK 1.1 = 45

我所使用的javac命令是jdk1.8的,而我所编译的目标文件是1.7的,所以会出这个问题;  
使用下面的编译命令可以解决编译的问题:

/jdk1.8/bin/javac -source 1.7 -target 1.7 T.java

但是这样是不被推荐的,虽然使用高版本的JDK可以通过指定编译source和target参数来兼容低版本JDK，但只是class文件格式上的，如果引用了高版本JRE库中某些方法一样会再低版本的JDK上报错；比如java.util.concurrent.ConcurrentHashMap.keySet()这个方法.

2.使用1编译命令,在编译后会报一个warning:  
![这里写图片描述][70 1]

warning: [options] bootstrap class path not set in conjunction with -source 1.7

在stackflow上发现问题的的解决在于可以设置编译参数.()

参考:  
[https://stackoverflow.com/questions/10382929/how-to-fix-java-lang-unsupportedclassversionerror-unsupported-major-minor-versi][https_stackoverflow.com_questions_10382929_how-to-fix-java-lang-unsupportedclassversionerror-unsupported-major-minor-versi]  
[https://blogs.oracle.com/darcy/new-javac-warning-for-setting-an-older-source-without-bootclasspath][https_blogs.oracle.com_darcy_new-javac-warning-for-setting-an-older-source-without-bootclasspath]  
[https://stackoverflow.com/questions/15882586/bootstrap-class-path-not-set/15882869][https_stackoverflow.com_questions_15882586_bootstrap-class-path-not-set_15882869]  
[https://blog.csdn.net/hudashi/article/details/7058998][https_blog.csdn.net_hudashi_article_details_7058998]

[70]: /images/20220525/623b6305b3704de4a3fc527311e46f57.png
[70 1]: /images/20220525/36f9178e89ee490cab42d2e26e99b4dc.png
[https_stackoverflow.com_questions_10382929_how-to-fix-java-lang-unsupportedclassversionerror-unsupported-major-minor-versi]: https://stackoverflow.com/questions/10382929/how-to-fix-java-lang-unsupportedclassversionerror-unsupported-major-minor-versi
[https_blogs.oracle.com_darcy_new-javac-warning-for-setting-an-older-source-without-bootclasspath]: https://blogs.oracle.com/darcy/new-javac-warning-for-setting-an-older-source-without-bootclasspath
[https_stackoverflow.com_questions_15882586_bootstrap-class-path-not-set_15882869]: https://stackoverflow.com/questions/15882586/bootstrap-class-path-not-set/15882869
[https_blog.csdn.net_hudashi_article_details_7058998]: https://blog.csdn.net/hudashi/article/details/7058998