In Java remote debugging, how to correctly obtain constant values ​​on remote servers?

Java remote debugging: Correctly obtain the remote server constant value

In Java remote debugging, developers often encounter a problem: the constant value obtained is not the value on the remote server, but the value of the local environment. This article will dig into this issue in depth and provide solutions.

Problem: Local constant value overrides remote value

During remote debugging, the constant value obtained during debugging is still the local compile-time value even if the constant class on the remote server has been updated. This is because the Java compiler optimizes constants and inlines them into the code. Therefore, the runtime does not read constant values ​​from the classes of the remote server.

Analysis: Compilation period optimization and constant inline

In order to improve performance, the Java compiler will embed constant values ​​directly into the code during the compilation stage. This means that even if the constant value on the remote server changes, the local code still uses the value that was determined at compile time.

Solution: Leverage remote debugging tools

To get the latest constant value on the remote server, you must use a remote debugging tool to avoid the impact of compiler optimization. The following steps are demonstrated using IntelliJ IDEA:

1. Server-side configuration: When starting a Java application on a remote server, add the following JVM parameters:

    -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005

   This will allow the server to listen for remote debug connections on port 5005. suspend=n means that the program does not pause and wait for the debugger to connect.

2. Local IDE configuration: In IntelliJ IDEA, configure the remote debug connection to connect to port 5005 of the server. This will allow the IDE to directly debug the code on the remote server, reading the actual constant value of its runtime. (Screenshots of IDEA remote debugging configuration interface should be inserted here, but they cannot be provided due to restrictions.)

In addition to IntelliJ IDEA, other IDEs or remote debugging tools (such as Alibaba Cloud's online debugging tools) can also achieve the same functions. These tools allow you to step through code in a remote environment, viewing the real-time values ​​of variables, including constants on the remote server.

By using the remote debugging tool, you can bypass compiler optimization and get the latest constant values ​​directly from the remote server, ensuring the accuracy of debug results. This is crucial for large distributed systems or applications that require frequent updates of constants.

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