为使用spring数据jpa和maven的项目创建一个可执行jar

Question

I am trying to execute a jar using java -jar <myJarName>

I tried multiple ways of creating this jar with dependencies

• First way

Added the "maven dependency" and the "maven jar" plugins to pom file

<build>
    <plugins>

        <plugin>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <phase>install</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${project.build.directory}/lib</outputDirectory>
                    </configuration>
                </execution>
            </executions>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <useDefaultManifestFile>true</useDefaultManifestFile>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <mainClass>fully.qualified.MainClass</mainClass>
                        <classpathPrefix>lib/</classpathPrefix>
                    </manifest>
                </archive>
            </configuration>
        </plugin>


    </plugins>
</build>

What was happening here is the the manifest contained all the class paths, but no dependencies got copied over

• Second way

Tried the "maven assembly plugin"

<build>
    <plugins>
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <configuration>
                <archive>
                    <manifest>
                        <mainClass>fully.qualified.MainClass</mainClass>
                    </manifest>
                </archive>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
            </configuration>
            <executions>
                <execution>
                    <id>make-assembly</id> <!-- this is used for inheritance merges -->
                    <phase>package</phase> <!-- bind to the packaging phase -->
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

A second jar ending in jar-with-dependencies got created that had everything I needed. But calling the jar fails with the error

Exception in thread "main" org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Unable to locate Spring NamespaceHandler for XML schema namespace [http://www.springframework.org/schema/data/jpa]
Offending resource: class path resource [META-INF/spring/app-context.xml]

        at org.springframework.beans.factory.parsing.FailFastProblemReporter.error(FailFastProblemReporter.java:70)
        at org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:85)

I verified that META-INF/Persistence.xml exists

• Third way

Tried the maven-shade-plugin

<build>
    <plugins>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>2.1</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals><goal>shade</goal></goals>
                    <configuration>
                        <transformers>
                            <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                <mainClass>fully.qualified.MainClass</mainClass>
                            </transformer>
                            <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                <resource>META-INF/spring.handlers</resource>
                            </transformer>
                            <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                <resource>META-INF/spring.schemas</resource>
                            </transformer>
                        </transformers>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

This one too copied all the dependencies, but it fails with an error

[main] INFO org.springframework.jdbc.datasource.DriverManagerDataSource - Loaded JDBC driver: org.h2.Driver
1022 [main] WARN org.springframework.context.support.ClassPathXmlApplicationContext - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in com.vmware.vra.performance.loganalyzer.Repository.JpaConfiguration: Invocation of init method failed; nested exception is java.lang.IllegalStateException: No persistence units parsed from {classpath*:META-INF/persistence.xml}
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in com.vmware.vra.performance.loganalyzer.Repository.JpaConfiguration: Invocation of init method failed; nested exception is java.lang.IllegalStateException: No persistence units parsed from {classpath*:META-INF/persistence.xml}

Answer 1

Just use SpringBoot. It's meant for generating a fat executable jar. You can use https://start.spring.io/ to create a SpringBoot project for Maven you can import your code into. As far as the conflicts go use the Spring BOM for Maven like this: https://www.baeldung.com/spring-maven-bom

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-framework-bom</artifactId>
            <version>4.3.8.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

It will ensure all your versions are consistent.

Answer 2

I went with the second option as well and had a similar problem. The issue you are running into is that you are combining multiple spring dependencies, which provide each definitions for factories, handlers, namespaces and such an you run into a conflict.

The way around this is to check all the spring dependencies for such definition and add them in your project by combining them. For more details you can take a look at this blog entry or at this maven module where I combined the configuration.