convert maven pom to gradle build - maven

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>

Answer 1

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.

Answer 2

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

Answer 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.

Answer 4

In the Gradle page:
Note Gradle doesn’t support the import scope in the POMs of dependencies, so you’ll have to manually import them using the above syntax.
https://gradle.org/migrating-a-maven-build-to-gradle/

Answer 5

Not only will the Gradle init task allow you to create a new skeleton project, but it will also automatically convert an existing Maven one to Gradle. All you have to do is run the command
$ gradle init