Run spring boot with jdk9 using jigsaw modules

Question

What's wrong with this application. I thought the mix of classpath jars and module jars are valid. For all jars not having an explicit module-info become an automatic module? When I delete my module-info.java it works. Because IDEA using the classpath for this case.

Java(TM) SE Runtime Environment (build 9+176)

IntelliJ IDEA 2017.1.4

module-info.java

module test {
    requires spring.boot.autoconfigure;
    requires spring.boot;
}

App.java

package com.foo.test;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class App {

    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}

pom.xml

<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.foo.test</groupId>
    <artifactId>test</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.M2</version>
    </parent>

    <name>test</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.9</maven.compiler.source>
        <maven.compiler.target>1.9</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/libs-milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>
</project>

Exception in thread "main" java.lang.IllegalArgumentException: Cannot instantiate interface org.springframework.context.ApplicationContextInitializer : org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.createSpringFactoriesInstances(SpringApplication.java:439) at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.getSpringFactoriesInstances(SpringApplication.java:418) at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.getSpringFactoriesInstances(SpringApplication.java:409) at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.(SpringApplication.java:266) at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.(SpringApplication.java:247) at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.run(SpringApplication.java:1245) at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.run(SpringApplication.java:1233) at test/com.foo.test.App.main(App.java:10) Caused by: java.lang.NoClassDefFoundError: java/sql/SQLException at spring.beans@5.0.0.RC2/org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:145) at spring.boot@2.0.0.M2/org.springframework.boot.SpringApplication.createSpringFactoriesInstances(SpringApplication.java:435) ... 7 more Caused by: java.lang.ClassNotFoundException: java.sql.SQLException at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:185) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496) ... 9 more

Answer 1

I assume spring.boot is an automatic module. An automatic module doesn't declare it dependences so you have to use --add-modules to ensure that any explicit modules needed are resolved. If spring.boot were an explicit module then I assume it would requires java.sql and you won't have this issue.

Answer 2

finally, I got it... my module-info have to look like this:

module test {
    requires java.sql; // my real problem solved with this
    requires spring.boot.autoconfigure;
    requires spring.boot;
    exports com.foo.test; // subsequent error 1: beeing accessible for some spring modules
    opens com.foo.test to spring.core; // subsequent error 2: beeing accessible for spring.core in a deep reflection way
}

Can someone explain why I have to requires java.sql; inside my own module when I don't use it?

Answer 3

This is almost certainly because you are missing the jdbc driver jar for MySql. you need to use this dependency :-

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>6.0.5</version>
</dependency>