convert maven pom to gradle build

Question

I am converting one of my maven project into gradle. For doing this I am runngin following command where pom.xml is located

gradle init --type pom

But it is giving me java.lang.NullPointerException

  FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':init'.
> Could not convert Maven POM /Users/myname/Documents/oAuth+Angular/workspace/feature-oauth_and_security_69/ui/pom.xml to a Gradle build.
> Unable to create Maven project model using POM /Users/myname/Documents/oAuth+Angular/workspace/feature-oauth_and_security_69/ui/pom.xml.
  > java.lang.NullPointerException (no error message)

is there anything to perform with init or anything else i am missing?

This is my pom.xml :

<?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>org.test</groupId>
<artifactId>ui</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>ui</name>
<description>Demo project for Spring Boot</description>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.2.2.RELEASE</version>
    <relativePath /> <!-- lookup parent from repository -->
</parent>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-parent</artifactId>
            <version>1.0.1.BUILD-SNAPSHOT</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-zuul</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-security</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.security.oauth</groupId>
        <artifactId>spring-security-oauth2</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-jwt</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <wro4j.version>1.7.6</wro4j.version>
    <java.version>1.7</java.version>
</properties>

<build>
    <resources>
        <resource>
            <directory>${project.basedir}/src/main/resources</directory>
        </resource>
        <resource>
            <directory>${project.build.directory}/generated-resources</directory>
        </resource>
    </resources>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
        <plugin>
            <artifactId>maven-resources-plugin</artifactId>
            <executions>
                <execution>
                    <!-- Serves *only* to filter the wro.xml so it can get an absolute 
                        path for the project -->
                    <id>copy-resources</id>
                    <phase>validate</phase>
                    <goals>
                        <goal>copy-resources</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${basedir}/target/wro</outputDirectory>
                        <resources>
                            <resource>
                                <directory>src/main/wro</directory>
                                <filtering>true</filtering>
                            </resource>
                        </resources>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>ro.isdc.wro4j</groupId>
            <artifactId>wro4j-maven-plugin</artifactId>
            <version>${wro4j.version}</version>
            <executions>
                <execution>
                    <phase>generate-resources</phase>
                    <goals>
                        <goal>run</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <wroManagerFactory>ro.isdc.wro.maven.plugin.manager.factory.ConfigurableWroManagerFactory</wroManagerFactory>
                <cssDestinationFolder>${project.build.directory}/generated-resources/static/css</cssDestinationFolder>
                <jsDestinationFolder>${project.build.directory}/generated-resources/static/js</jsDestinationFolder>
                <wroFile>${project.build.directory}/wro/wro.xml</wroFile>
                <extraConfigFile>${basedir}/src/main/wro/wro.properties</extraConfigFile>
                <contextFolder>${basedir}/src/main/wro</contextFolder>
            </configuration>
            <dependencies>
                <dependency>
                    <groupId>org.webjars</groupId>
                    <artifactId>jquery</artifactId>
                    <version>2.1.1</version>
                </dependency>
                <dependency>
                    <groupId>org.webjars</groupId>
                    <artifactId>angularjs</artifactId>
                    <version>1.3.8</version>
                </dependency>
                <dependency>
                    <groupId>org.webjars</groupId>
                    <artifactId>bootstrap</artifactId>
                    <version>3.2.0</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

<repositories>
    <repository>
        <id>spring-snapshots</id>
        <name>Spring Snapshots</name>
        <url>http://repo.spring.io/libs-snapshot-local</url>
        <snapshots>
            <enabled>true</enabled>
        </snapshots>
    </repository>
    <repository>
        <id>spring-milestones</id>
        <name>Spring Milestones</name>
        <url>http://repo.spring.io/libs-milestone-local</url>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>
    <repository>
        <id>spring-releases</id>
        <name>Spring Releases</name>
        <url>http://repo.spring.io/libs-release-local</url>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>
</repositories>

Solution 1

I don't know why but worked after commenting the "repositories" Thanks for all help

Solution 2

There is a problem with <parent> element, exactly with <relativePath/> inner element in block:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.2.2.RELEASE</version>
    <relativePath />
</parent>

When you remove the <relativePath/> element or set it correctly, the gradle will initialize the project.

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.2.2.RELEASE</version>
    <!-- <relativePath>../parent/pom.xml</relativePath> -->
</parent>

The problem was with the incorrectly set relativePath element, which didn't point to the parent pom file as it should.

Solution 3

I feel a cleaner way to convert a maven project with parent module to a gradle one is by following steps below:

• Get an effective pom.xml for the project to pom_eff.xml:
  mvn help:effective-pom -Doutput=pom_eff.xml
• Remove parent tag from pom_eff.xml
• Take backup of the original pom.xml and rename pom_eff.xml to pom.xml.
• Do gradle init

This way gradle engine gets a flattened version of the pom.xml that is far simpler to decode for the gradle system.

Comments

[Mike D]

is it possible for you to post your POM file?

[Mike D]

Removing the repositories doesn't work, as I've just tried. Nor does the relativePath parent solution mentioned. Consider 1- this is an incubating feature, 2- specifying the versions of tools your are using via gradle -v

[John Zhang]

I don't have the <relativePath> but still failed. I tried to delete <repositories> but it doesn't help.

[John Zhang]

Removing the repositories doesn't work for me either.

[John Zhang]

This works for me but I need to remove the <projects> tag in the pom_eff.xml.

[Marian Klühspies]

Not doing anything at all with the dependencies in my case

[Heinz]

gradle inti doesn't do anything for the dependencies defined in the root project POM file, so all subprojects fail

[Heinz]

running gradle build afterwards does not do anything