How to add a dependency to a Spring Boot Jar in another project?

问题

I have a Spring Boot application and I have created a Jar out of that. Following is my pom.xml:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-mail</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
    <dependency>
        <groupId>org.thymeleaf.extras</groupId>
        <artifactId>thymeleaf-extras-java8time</artifactId>
        <version>2.1.0.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
    <!-- WebJars -->
    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>mail</artifactId>
        <version>1.4.7</version>
    </dependency>
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.6.2</version>
    </dependency>
</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

I want to use this Jar in my other application so added this jar to my application. But when I am calling a method in that Jar, it is throwing a ClassNotFoundException.

How can I fix this issue? How can I add a dependency to a Spring Boot JAR?

回答1:

By default, Spring Boot repackages your JAR into an executable JAR, and it does that by putting all of your classes inside BOOT-INF/classes, and all of the dependent libraries inside BOOT-INF/lib. The consequence of creating this fat JAR is that you can no longer use it as a dependency for other projects.

From Custom repackage classifier:

By default, the repackage goal will replace the original artifact with the repackaged one. That's a sane behaviour for modules that represent an app but if your module is used as a dependency of another module, you need to provide a classifier for the repackaged one.

The reason for that is that application classes are packaged in BOOT-INF/classes so that the dependent module cannot load a repackaged jar's classes.

If you want to keep the original main artifact in order to use it as a dependency, you can add a classifier in the repackage goal configuration:

<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  <version>1.4.1.RELEASE</version>
  <executions>
    <execution>
      <goals>
        <goal>repackage</goal>
      </goals>
      <configuration>
        <classifier>exec</classifier>
      </configuration>
    </execution>
  </executions>
</plugin>

With this configuration, the Spring Boot Maven Plugin will create 2 JARs: the main one will be the same as a usual Maven project, while the second one will have the classifier appended and be the executable JAR.

回答2:

Tunaki's answer is correct but doesn't work in Spring Boot 2.

Spring Boot 1.x

  <plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <version>1.5.20.RELEASE</version>
    <executions>
      <execution>
        <goals>
          <goal>repackage</goal>
        </goals>
        <configuration>
          <classifier>exec</classifier>
        </configuration>
      </execution>
    </executions>
    ...
  </plugin>

If you are using spring-boot-starter-parent, the repackage goal is executed automatically in an execution with id repackage. In that setup, only the configuration should be specified as shown in the following example:

  <plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <executions>
      <execution>
        <id>repackage</id>
        <configuration>
          <classifier>exec</classifier>
        </configuration>
      </execution>
    </executions>
    ...
  </plugin>

回答3:

What @Tunaki stated was mostly correct but the one missing part based on your original question was:

This throwing ClassNotFoundException. The External jar's used in spring boot application is missing.

This is due to the fact that the FatJAR created from the maven packaging has the dependent libraries specified in a specific location that works for how Spring Boot executes the application. If you are just adding the JAR to another application's classpath then you should do what @Tunaki said and also include the dependent JAR files to the classpath. The best way to work with this is to use the Maven Dependency Plugin specifically targetting the dependency:copy-dependencies mojo to download all the dependencies into a folder that you can then specify as a library path when compiling the other application.

回答4:

You can extend your project by maven-assembly-plugin

<plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>3.1.0</version>
        <configuration>
        <descriptorRefs>
                <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
        </configuration>
        <executions>
        <execution>
            <id>make-assembly</id>
            <phase>package</phase>
            <goals>
            <goal>single</goal>
            </goals>
            </execution>
        </executions>
</plugin>

After the build you will get 3 jars. The main one will be the same as a usual Maven project, while the second one will have the classifier appended with exec and be the executable JAR. The third jar name will be appended by jar-with-dependencies and will contain your classes with classes added as dependencies in your spring boot application(spring-boot-starter-web, thymeleaf,...), so into the pom of the application where you want to add that project as dependencie you won't have to add dependencies from spring boot project.

回答5:

For Spring Boot 2 @Tunaki's answer must be modified a bit according to the documentation if spring-boot-starter-parent is used as parent :

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <executions>
      <execution>
        <id>repackage</id>
        <configuration>
          <classifier>exec</classifier>
        </configuration>
      </execution>
    </executions>

Take note of the extra <id>repackage</id> necessary to overwrite to execution from the spring-boot-starter-parent.

回答6:

You can setup your projects so that the batch launcher relies on a jar, which would be shared with your other application.

Said differently, as per your initial request :

I want to use this Jar in my other application so added this jar to my application.

Let's say your jar is your project A, and your application is your project B.

Now, what I suggest, is that you remove the launching part from A ; then you put it into a new project C, that would embed Spring Boot, and that would rely almost totally on A.

Then, since A is now a simple jar, B can use it as a dependency.

回答7:

Use the build section provided below, it will do three things:

Create the spring boot jar using spring-boot-maven-plugin
Create a normal jar with your source code compiled classes using maven-assembly-plugin
Install the normal jar into the m2 folder locally

If you want to deploy the normal jar into a remote repository, configure the deploy plugin

<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-assembly-plugin</artifactId>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                    <configuration>
                        <appendAssemblyId>true</appendAssemblyId>
                        <descriptors>
                            <descriptor>src/main/resources/sources-jar-build.xml</descriptor>
                        </descriptors>
                        <finalName>${pom.artifactId}-${pom.version}</finalName>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
             <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-install-plugin</artifactId>
            <executions>
                <execution>
                    <id>install-file</id>
                    <goals>
                        <goal>install-file</goal>
                    </goals>
                    <configuration>
                        <file>${pom.artifactId}-${pom.version}</file>
                        <artifactId>${pom.artifactId}</artifactId>
                        <groupId>${pom.groupId}</groupId>
                        <version>${pom.version}</version>
                    </configuration>
                </execution>
            </executions>               
        </plugin>
    </plugins>
</build>

Place the below content in a file named "sources-jar-build.xml", into resources folder:

<assembly
    xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">
    <id>sources</id>
    <includeBaseDirectory>false</includeBaseDirectory>

    <formats>
        <format>jar</format>
    </formats>
    <fileSets>
        <fileSet>
            <directory>${project.basedir}/target/classes</directory>
            <outputDirectory>/</outputDirectory>
        </fileSet>
    </fileSets>
</assembly>

回答8:

any project if you want add as a dependency you need that project <groupId>,<artifactId>,<version>, with these details you can add your project as a dependency in another module or application for ex: your application pom details

<project 
        <groupId>com.sample</groupId>
        <artifactId>sampleapp</artifactId>
        <version>1.0</version>
        <packaging>jar</packaging>
</project>`

your dependency as like below

 <dependency>
 <groupId>com.sample</groupId>
 <artifactId>sampleapp</artifactId>
 <version>1.0</version>
</dependency>

来源：https://stackoverflow.com/questions/40089443/how-to-add-a-dependency-to-a-spring-boot-jar-in-another-project

标签

maven

spring-boot

jar

spring-boot-maven-plugin