ClassNotFoundException 和 NoClassDefFoundError 尝试使用 java.lang.reflect 检查 Spring Boot jar 文件

发布于 2025-01-10 18:03:50 字数 1750 浏览 0 评论 0原文

我正在尝试构建一个工具，可以检查打包为 jar 的指定 Spring Boot 应用程序。我能够列出 jar 的内容，并且我能够加载和检查一些类，但其他类，最重要的是我们自己的类 - 那些构成实际应用程序代码的类 - 我无法检查并获取 ClassNotFoundException 尝试加载它们时。这些类中的许多（但不是全部）都位于 BOOT-INF/classes 中，我尝试过在提供的 URL 中使用或不使用该路径，以及使用或不使用该路径作为类名的一部分。我还收到许多 NoClassDefFoundError 异常。如果我展开 jar 文件，“丢失”的类位于 BOOT-INF/classes/ 下的预期位置，

我不尝试运行该应用程序。这与 ./gradlew bootrun 配合得很好，我并没有尝试创建自定义启动器或类似的东西，这就是我能够找到的示例代码。即使是 SO 建议也都与运行和部署 Spring Boot 应用程序的问题有关。我确信原因是相似或相关的，但我不知道如何弥合差距。

我想要做的就是提取所有具有 @Value 注释的参数，并为我们的代码和任何依赖项报告这些注释的值。最终，我希望能够验证我们的 yaml 配置并报告这些文件中缺少的配置值。

清单（稍作编辑）：

Manifest-Version: 1.0
Spring-Boot-Classpath-Index: BOOT-INF/classpath.idx
Spring-Boot-Layers-Index: BOOT-INF/layers.idx
Start-Class: com.redacted.redacted.redacted.redacted.redactedApp
 lication
Spring-Boot-Classes: BOOT-INF/classes/
Spring-Boot-Lib: BOOT-INF/lib/
Spring-Boot-Version: 2.5.8
Specification-Version: 1.0.0
Main-Class: org.springframework.boot.loader.JarLauncher

我的类加载器是这样创建的：

final URL url = jarFile.getUrl();
final URLClassLoader urlClassLoader = LaunchedURLClassLoader.newInstance(new URL[] {
    new URL(url.toString() + "BOOT-INF/classes!/"),
    url,
});

我获取类名并尝试加载（未显示异常处理代码）：

String name = jarEntry.getName();
int endIndex = name.lastIndexOf(".class");

String className = name.substring(0, endIndex)
        .replace('/', '.').replace("BOOT-INF.classes.", "");

Class<?> loadedClass = urlClassLoader.loadClass(className);

如何解决加载这些类的问题，或者，是否有另一种方法使用 @Value 注释提取所有代码和依赖项的所有参数？

原文

I am trying to build a tool that can inspect a specified Spring Boot application packaged as a jar. I am able to list the contents of the jar, and I am able to load and inspect some classes, but others, most importantly our own classes -- those that make up the actual application code -- I cannot inspect and get a ClassNotFoundException when trying to load them. Many, but not all, of those classes are located in BOOT-INF/classes and I have tried both with and without that path in the URLs provided, and with and without that as part of the class name. I also get many NoClassDefFoundError exceptions. If I expand the jar file, the "missing" classes are located where expected under BOOT-INF/classes/

I am not trying to run the application. That works fine with ./gradlew bootrun and I am not trying to create a custom launcher or anything like that, which is all I'm able to find for sample code. Even the SO suggestions are all related to issues running and deploying Spring Boot applications. I'm sure the causes are similar or related, but I don't know how to bridge the gap.

All I want to do is extract all the parameters that have the @Value annotation and report the values of those annotations, for both our code and any dependencies. Ultimately I want to be able to validate our yaml configurations and report on missing configuration values that are missing from those files.

Manifest (lightly redacted):

Manifest-Version: 1.0
Spring-Boot-Classpath-Index: BOOT-INF/classpath.idx
Spring-Boot-Layers-Index: BOOT-INF/layers.idx
Start-Class: com.redacted.redacted.redacted.redacted.redactedApp
 lication
Spring-Boot-Classes: BOOT-INF/classes/
Spring-Boot-Lib: BOOT-INF/lib/
Spring-Boot-Version: 2.5.8
Specification-Version: 1.0.0
Main-Class: org.springframework.boot.loader.JarLauncher

My class loader is created like this:

final URL url = jarFile.getUrl();
final URLClassLoader urlClassLoader = LaunchedURLClassLoader.newInstance(new URL[] {
    new URL(url.toString() + "BOOT-INF/classes!/"),
    url,
});

I get the class name and try to load (exception handling code not shown):

String name = jarEntry.getName();
int endIndex = name.lastIndexOf(".class");

String className = name.substring(0, endIndex)
        .replace('/', '.').replace("BOOT-INF.classes.", "");

Class<?> loadedClass = urlClassLoader.loadClass(className);

How can I fix the problem loading these classes, or, alternatively, is there another way to extract all parameters with the @Value annotation, for all code and dependencies?

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