In Java projects, the following key points are needed to effectively use Maven or Gradle dependency management: 1. Understand dependency delivery and scope, and reasonably set the scope of compile, runtime, test, etc. to avoid redundant dependencies; 2. Unify the version number, centrally manage it through Maven's properties or Gradle's versions.gradle, and use BOM to unify the dependency set version; 3. Use tools such as mvn dependency:tree or gradle dependencies to troubleshoot conflicts, and resolve conflicts by explicitly specifying the version, excluding dependencies or force policies; 4. In multi-module projects, Maven uses the parent POM and Gradle to uniformly configure it through the root build.gradle to realize dependency sharing and avoid duplicate and circular dependencies.

In Java projects, dependency management is a very core part of the development process. Maven and Gradle are two of the most mainstream build tools at present, and they both provide powerful dependency management capabilities. If used well, it can improve the clarity of the project structure and simplify version control; if used poorly, it may lead to version conflicts and construction failures. Let’s start from several practical scenarios and talk about how to use Maven or Gradle more effectively to manage dependencies.

1. Understand dependency delivery and scope

Whether it is Maven or Gradle, they support transitive dependencies, which means that when you introduce a library, the other libraries it depends on will also be automatically pulled out. But this can also lead to dependency confusion, especially when different libraries refer to different versions of the same library.

• In Maven , the scope of dependencies is defined through <scope></scope> tag, such as compile , runtime , test , etc.
• Gradle is managed using configuration, such as implementation , testImplementation , runtimeOnly , etc.

For example: you use Spring Boot's starter, which already contains the Tomcat embedded container, and the default is the runtime scope. If you just want to use it during testing, you can change its dependency testRuntimeOnly .

Rational use of scope can avoid packaging unnecessary dependencies into the final application and reduce the risk of conflict.

2. Unified version number and dependency upgrade strategy

As the project grows bigger and more dependencies, it becomes cumbersome to manually maintain the version of each library. At this time, you need to manage the version number uniformly:

• Maven can define version variables in <properties></properties> and then reference them in each dependency.
• Gradle can define variables in build.gradle or separate versions.gradle files, and can even centrally manage recommended versions through plugins such as nebula.dependency-recommender .

Suggested practices:

• Use the BOM (Bill of Materials) file to uniformly manage a set of related dependencies, and Spring and many open source projects provide BOM.
• Regularly check whether a new version is available, and PR can be initiated automatically with tools such as Dependabot or Renovate.

3. Practical skills to resolve dependency conflicts

Dependency conflict is a common problem, manifested as exceptions such as the runtime class not found and the method does not exist. The key to troubleshooting this type of problem is to see which version is finally used.

• Maven can use mvn dependency:tree to view the complete dependency tree.
• Gradle uses gradle dependencies to output dependencies.

Once a conflict is discovered, there are several ways to deal with it:

• Explicitly specify a version to "overwrite" the default selection.
• Exclude some unwanted dependencies, such as using <exclusion></exclusion> or exclude group: 'xxx', module: 'yyy' .
• Use a forced versioning strategy ( force = true in Gradle).

For example, if multiple libraries rely on different versions of Guava, you can choose a stable version and set it to force.

4. Dependency management for building multi-module projects

For large projects, it is usually split into multiple modules. At this time, you need to consider how to share dependency configurations between modules.

• Maven supports the concept of parent POM and defines common dependencies and plug-in configurations in the parent module.
• Gradle can be configured uniformly in the root build.gradle using subprojects or allprojects .

Suggested practices:

• Put public dependencies in parent or base modules to avoid repeated declarations.
• Each submodule only declares its own unique dependencies.
• Pay attention to the dependency order between modules and avoid circular dependencies.

Basically that's it. Dependency management may seem simple, but details are easily overlooked in actual projects. Whether using Maven or Gradle, mastering these points can make your project cleaner and more stable.

The above is the detailed content of Managing Dependencies with Java Maven or Gradle. For more information, please follow other related articles on the PHP Chinese website!