这里有详细的解释:

https://github.com/spring-projects/spring-ide/issues/78

只是为了将来参考，这是答案的相关部分(忽略引用Spring Boot应用程序的事实，在许多其他情况下行为是相同的):

Whenever you set a breakpoint in Eclipse/STS, the IDE tries to set the breakpoint in the VM if you launch an app. That is what happens in your case when you run the boot app in debug mode. For each class that gets loaded into the JVM, the IDE checks whether it needs to set a breakpoint or not. If it decides to set the breakpoint, the tries to do so (using the information from the breakpoint definition in the IDE, including its line number, since you usually set line breakpoints on a source file at a given line). This decision (whether to set the breakpoint on a given loaded class or not) checks the types that you set the breakpoint on, enclosing types, and inner classes. This makes sure that breakpoints for inner classes (even anonymous inner classes) are set to the JVM (and are not ignored). Spring Boot generates an inner class for your controller at runtime (this is the CGLIB generated inner class that appears in the error message). When the JVM loads that class, it tries to set the line number breakpoint of the enclosing type (for this inner class). Since the generated inner class doesn't have any line number information (it doesn't need to have line number information), setting the breakpoint fails for this inner class with the mentioned error message. When the IDE loads the enclosing type (your controller class itself), it also tries to set the line breakpoint and succeeds with that. This is visualized with the check marker on the breakpoint marker. Therefore you can safely ignore the error message that shows up. To avoid this error message to show up, you can go to the preferences (Java -> Debug) and disable "Warn when unable to install breakpoint due to missing line number attributes".

If someone is trying to debug Java's source code, then, this is the only solution that worked for me. Most of the above answers talk about setting the Compiler option to generate line numbers.But, if want to debug Java's source code (say java.util.HashMap), then the above options may not work for you. This is because , the project from where you intend to debug the source code is having the Java Build Path --> Library --> JRE System Library pointing to the jre jar instead of the jdk jar. The classes bundled inside jre jar have already been pre-compiled with a specific option, that will not honor the Compiler option settings. Solution, is to reconfigure your project to have the JRE System Library point to the jdk jar. The classes inside your jdk jar will honour the Compiler option settings. So, once you update your project's JRE System Library to point to the jdk jar, debug on Java source code will start working.

在使用Spring Tool Suite (STS)启动Java EE项目时，我们也会遇到这个消息，但是我们可以忽略这个消息，因为一切都很好。

我从黑莓SDK方面得到了这个问题的答案:出于某种原因，无论我在编译器中修改了多少次选项，实际的底层设置文件都没有改变。

在项目的.settings文件夹中查找一个名为org.eclipse.jdt.core.prefs的文件。

在那里你可以手动修改设置:

org.eclipse.jdt.core.compiler.debug.lineNumber=generate

编辑:除此之外，我还注意到有时我可以忽略Eclipse给出的警告，它仍然会停在需要的地方……越来越奇怪……我将此归入我们作为开发人员所需要处理的事情中。

这里有详细的解释:

https://github.com/spring-projects/spring-ide/issues/78

只是为了将来参考，这是答案的相关部分(忽略引用Spring Boot应用程序的事实，在许多其他情况下行为是相同的):

Whenever you set a breakpoint in Eclipse/STS, the IDE tries to set the breakpoint in the VM if you launch an app. That is what happens in your case when you run the boot app in debug mode. For each class that gets loaded into the JVM, the IDE checks whether it needs to set a breakpoint or not. If it decides to set the breakpoint, the tries to do so (using the information from the breakpoint definition in the IDE, including its line number, since you usually set line breakpoints on a source file at a given line). This decision (whether to set the breakpoint on a given loaded class or not) checks the types that you set the breakpoint on, enclosing types, and inner classes. This makes sure that breakpoints for inner classes (even anonymous inner classes) are set to the JVM (and are not ignored). Spring Boot generates an inner class for your controller at runtime (this is the CGLIB generated inner class that appears in the error message). When the JVM loads that class, it tries to set the line number breakpoint of the enclosing type (for this inner class). Since the generated inner class doesn't have any line number information (it doesn't need to have line number information), setting the breakpoint fails for this inner class with the mentioned error message. When the IDE loads the enclosing type (your controller class itself), it also tries to set the line breakpoint and succeeds with that. This is visualized with the check marker on the breakpoint marker. Therefore you can safely ignore the error message that shows up. To avoid this error message to show up, you can go to the preferences (Java -> Debug) and disable "Warn when unable to install breakpoint due to missing line number attributes".

这解决了我的问题:

窗口->首选项->服务器->运行时环境 Apache Tomcat ->编辑 选择JDK而不是JRE