How to use a Java class from an application in another application?

Question

I have a class in an application (it is a Spring Boot project), for example:

package com.exemple.spring.springboot.model;

public class Employee {
   ...
}

And in the pom.xml I have this:

<?xml version="1.0" encoding="UTF-8"?>
<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">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.exemple.spring</groupId>
    <artifactId>spring-boot</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    ...

Now I want to use this class Employee in another application like this:

package com.exe.spring.controller;

import org.springframework.stereotype.Controller;
import com.exemple.spring.springboot.model.Employee;


@Controller
public class EmployeeController {

    public Employee getAnEmployee() {
       ...
    }
}

I've build the JAR with mvn clean install for the first app and I've added it in the pom.xml of the second app like this:

<?xml version="1.0" encoding="UTF-8"?>
<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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.exe.spring</groupId>
    <artifactId>rest-client</artifactId>
    <version>1.0-SNAPSHOT</version>
    <name>rest-client</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>com.exemple.spring</groupId>
            <artifactId>spring-boot</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>

    </dependencies>

And the problem is that I cannot import the Employee class in the EmployeeController class. I've imported it manually like this import com.exemple.spring.springboot.model.Employee;, but Intellij show me an error: Cannot resolve symbol 'springboot'. I see that the dependency is presented in the local repository. It is very weird because Eclipse doens't see anything to import for Employee, and Intellij see the class but when I try to click on "Import class" it doesn't import anything. What can I do to import it correctly? Thank you!

score 0 · Answer 1 · answered Aug 24 '19 at 13:58

0

You can not directly add it as dependency, it has to be present in one of certral/ local / remote repository.

You need to add the jar to repo, e.g. local repoository,

mvn install:install-file -DlocalRepositoryPath=repo -DcreateChecksum=true -Dpackaging=jar -Dfile=[your-jar] -DgroupId=[...] -DartifactId=[...] -Dversion=[...]

And then add repository as,

<repository>
    <id>repo</id>
    <url>file://${project.basedir}/repo</url>
</repository>

Check other optios here

answered Aug 24 '19 at 13:58

Vikas

6,868
4
27
41

Thank you for the reply, but I've did mvn clean install for the first app, and I see that it is presented in the local repository, and then I simply add the dependency in the pom.xml of the 2nd app. Isn't it enough? – Yuan Aug 24 '19 at 14:11
That is enough. – J Fabian Meier Aug 24 '19 at 19:17

score 0 · Answer 2 · answered Aug 24 '19 at 14:14

Check follow:

You've used mvn clean install to build and install the first JAR.
You have your JAR in the classpath of the second app. You can see all of them in "External libraries" in idea. If not, reimport maven project or use auto-import option

Also you can use different maven project structure e.g :

Common parent
 |
 |-------> first jar 
 |
 |-------> second jar (with first one as a dependency)

I think it should work better for you.

How to use a Java class from an application in another application?

2 Answers2