How to use the command 'jdeps' (with examples)

jdeps is a command-line tool provided by Oracle that analyzes the dependencies of Java class files or Java archive (JAR) files. It helps developers understand and manage the dependencies within their Java applications.

Use case 1: Analyze the dependencies of a .jar or .class file

Code:

jdeps path/to/filename.class

Motivation:

Analyzing the dependencies of a Java class file is essential for understanding the runtime behavior of the class and identifying any potential issues with its dependencies. By using jdeps, developers can gain insights into which classes or packages are being used by a specific class file.

Explanation:

• jdeps: The command to run the jdeps tool.
• path/to/filename.class: Specifies the path to the target .class file for which you want to analyze the dependencies.

Example output:

path/to/filename.class -> java.util
path/to/filename.class -> java.lang
...

Use case 2: Print a summary of all dependencies of a specific .jar file

Code:

jdeps path/to/filename.jar -summary

Motivation:

Printing a summary of the dependencies of a specific JAR file provides an overview of the external dependencies used by the application. This information can be helpful for managing and troubleshooting the dependencies of the application.

Explanation:

• jdeps: The command to run the jdeps tool.
• path/to/filename.jar: Specifies the path to the target JAR file for which you want to analyze the dependencies.
• -summary: An option to print a summary of the dependencies.

Example output:

path/to/filename.jar -> java.util
path/to/filename.jar -> org.apache.commons.lang3
...

Use case 3: Print all class-level dependencies of a .jar file

Code:

jdeps path/to/filename.jar -verbose

Motivation:

By printing all class-level dependencies of a JAR file, developers can get a detailed view of the dependencies at the class level. This can be useful to identify specific classes within the application that have certain dependencies or identify potential issues related to class dependencies.

Explanation:

• jdeps: The command to run the jdeps tool.
• path/to/filename.jar: Specifies the path to the target JAR file for which you want to analyze the dependencies.
• -verbose: An option to print all class-level dependencies.

Example output:

path/to/filename.jar -> com.example.DependencyClass
path/to/filename.jar -> com.example.anotherpackage.OtherDependencyClass
...

Use case 4: Output the results of the analysis in a DOT file into a specific directory

Code:

jdeps path/to/filename.jar -dotoutput path/to/directory

Motivation:

Generating a DOT file representing the dependencies can be helpful for visualizing the dependencies between classes within a Java application. By specifying the output directory, developers can easily locate and use the generated DOT file.

Explanation:

• jdeps: The command to run the jdeps tool.
• path/to/filename.jar: Specifies the path to the target JAR file for which you want to analyze the dependencies.
• -dotoutput: An option to specify the directory where the DOT file will be generated.
• path/to/directory: Specifies the path to the directory where the DOT file will be generated.

Example output:

Generating DOT file: path/to/directory/filename.dot

Use case 5: Display help

Code:

jdeps --help

Motivation:

When using a new or unfamiliar command, it is often helpful to have access to documentation or help information. The --help option provides a quick way to access the jdeps command’s help information.

Explanation:

• jdeps: The command to run the jdeps tool.
• --help: An option to display the command help.

Example output:

Usage: jdeps <options> <classes ...>
where options include:
    ...
    --help             Displays usage information (this message).
    ...

Conclusion:

The jdeps command is a useful tool for analyzing the dependencies of Java class files or JAR files. By using jdeps, developers can gain insights into the dependencies within their applications, troubleshoot dependency-related issues, and visualize class dependencies using DOT files.