java实现读取jar包中配置文件的几种方式

public interface JarReader {
   /**
     * 读取jar包中的文件
     * @param jarPath   jar包路径
     * @param file  jar包中的文件路径
     * @return  文件内容，转换成字符串了，其它需求也可以转换成输入流。
     * @throws IOException
     */
    String readFromJar(String jarPath,String file) throws IOException;
}

JarFile是java自带的一种读取jar包的API，很多人应该用过，我就直接贴代码了。public class JarFileJarReader implements JarReader {
    @Override
    public String readFromJar(String jarPath,String file) throws IOException {
        JarFile jarFile=null;
        try {
            jarFile=new JarFile(jarPath);
            JarEntry jarEntry=jarFile.getJarEntry(file);
            InputStream input=jarFile.getInputStream(jarEntry);
            return IOUtils.toString(input,"UTF-8");
        } catch (IOException e) {
            throw e;
        } finally {
            IOUtils.closeQuietly(jarFile);
        }
    }
}

public void getManiFest(String jarPath) throws IOException {
        JarFile jarFile=null;
        try {
            jarFile=new JarFile(jarPath);
            Manifest manifest=jarFile.getManifest();
            if (manifest!=null){
                //获取Class-Path
                String classPaths = (String) manifest.getMainAttributes().get(new Attributes.Name("Class-Path"));
                if (classPaths != null && !classPaths.isEmpty()) {
                    String[] classPathArray = classPaths.split(" ");
                }
                //获取JDK版本
                String jdkVersion = (String) manifest.getMainAttributes().get(new Attributes.Name("Build-Jdk"));
                //还可以获取其它内容，比如Main-Class等等
            }
        } catch (IOException e) {
            throw e;
        } finally {
            IOUtils.closeQuietly(jarFile);
        }
    }

public class URLJarReader implements JarReader {
    @Override
    public String readFromJar(String jarPath, String file) throws IOException {
        JarURLConnection jarURLConnection=null;
        try {
            URL fileUrl=ParseUtil.fileToEncodedURL(new File(jarPath));
            URL jarUrl=new URL("jar", "", -1, fileUrl + "!/");
            URL moduleUrl = new URL(jarUrl, ParseUtil.encodePath(file, false));
            jarURLConnection = (JarURLConnection)moduleUrl.openConnection();
            return IOUtils.toString(jarURLConnection.getInputStream(),"UTF-8");
        } catch (IOException e) {
            throw e;
        } finally {
            if (jarURLConnection!=null){
                try {
                    jarURLConnection.getJarFile().close();
                } catch (IOException ignore) {
                }
            }
        }
    }
}

public class ClassLoaderJarReader implements JarReader {
    @Override
    public String readFromJar(String jarPath, String file) throws IOException{
        URLClassLoader urlClassLoader=null;
        try {
            URL fileUrl=ParseUtil.fileToEncodedURL(new File(jarPath));
            urlClassLoader=new URLClassLoader(new URL[]{fileUrl},null);
            InputStream inputStream=urlClassLoader.getResourceAsStream(file);
            if (inputStream==null){
                throw new FileNotFoundException("not find file:"+file+" in jar:"+jarPath);
            }else{
                return IOUtils.toString(inputStream,"UTF-8");
            }
        } catch (IOException e) {
            throw e;
        } finally {
            IOUtils.closeQuietly(urlClassLoader);
        }
    }
}