Spring Boot : java.lang.NoClassDefFoundError: javax/mail/MessagingException

Exception in thread "main" java.lang.NoClassDefFoundError: javax/mail/MessagingException
Caused by: java.lang.ClassNotFoundException: javax.mail.MessagingException
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: MasterProcess.  Program will exit.
This may happen if you accedentaly add other javax.mail maven dependency into your pom.xml:

1. <dependency>
2. <groupId>javax.mail</groupId>
3. <artifactId>mail</artifactId>
4. <version>1.4</version>
5. </dependency>

but in Spring-Boot the actual dependency is:

1. <dependency>
2. <groupId>org.springframework.boot</groupId>
3. <artifactId>spring-boot-starter-mail</artifactId>
4. </dependency>

Goto: http://start.spring.io/

try creating maven project with javax mail dependency and examine the pom.xml. You will find some dependecies like this:

1. <?xml version="1.0" encoding="UTF-8"?>
2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3.     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.     <modelVersion>4.0.0</modelVersion>
6.     <groupId>com.example</groupId>
7.     <artifactId>skeleton</artifactId>
8.     <version>0.0.1-SNAPSHOT</version>
9.     <packaging>jar</packaging>
11.     <name>demo</name>
12.     <description>Demo project for Spring Boot</description>
14.     <parent>
15.         <groupId>org.springframework.boot</groupId>
16.         <artifactId>spring-boot-starter-parent</artifactId>
17.         <version>1.4.0.RELEASE</version>
18.         <relativePath/> <!-- lookup parent from repository -->
19.     </parent>
21.     <properties>
22.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
23.         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
24.         <java.version>1.8</java.version>
25.     </properties>
27.     <dependencies>
28.         <dependency>
29.             <groupId>org.springframework.boot</groupId>
30.             <artifactId>spring-boot-starter-mail</artifactId>
31.         </dependency>
33.         <dependency>
34.             <groupId>org.springframework.boot</groupId>
35.             <artifactId>spring-boot-starter-test</artifactId>
36.             <scope>test</scope>
37.         </dependency>
38.     </dependencies>
40.     <build>
41.         <plugins>
42.             <plugin>
43.                 <groupId>org.springframework.boot</groupId>
44.                 <artifactId>spring-boot-maven-plugin</artifactId>
45.             </plugin>
46.         </plugins>
47.     </build>
50. </project>

Spring Boot : Generate new maven project via Spring Boot

Spring Boot awsome CLI tool lets get start with new template project real quick :)

Go to http://start.spring.io/

Set group and package names,packaging(standalone(jar) or web(war)),project type(maven orgradle).

You can also select java version,language(java or groovy) and pre-add lots of dependencies(jpa,template engin,AOP and lote more :) ).

Click Generate project button and  project will be downloaded as zip :)

Doing it in shell/command prompt:
so that we can get it done via script:

1. #generate & download
2. spring init --build=maven --java-version=1.8 --dependencies=mail --packaging=jar skeleton.zip
3. #unzip
4. unzip skeleton.zip
5. #remove zip
6. rm -f skeleton.zip
7. #we have our project in current directory :)
8. cat pom.xml

look at the generated pom.xml:-

1. <?xml version="1.0" encoding="UTF-8"?>
2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3.     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.     <modelVersion>4.0.0</modelVersion>
6.     <groupId>com.example</groupId>
7.     <artifactId>skeleton</artifactId>
8.     <version>0.0.1-SNAPSHOT</version>
9.     <packaging>jar</packaging>
11.     <name>demo</name>
12.     <description>Demo project for Spring Boot</description>
14.     <parent>
15.         <groupId>org.springframework.boot</groupId>
16.         <artifactId>spring-boot-starter-parent</artifactId>
17.         <version>1.4.0.RELEASE</version>
18.         <relativePath/> <!-- lookup parent from repository -->
19.     </parent>
21.     <properties>
22.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
23.         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
24.         <java.version>1.8</java.version>
25.     </properties>
27.     <dependencies>
28.         <dependency>
29.             <groupId>org.springframework.boot</groupId>
30.             <artifactId>spring-boot-starter-mail</artifactId>
31.         </dependency>
33.         <dependency>
34.             <groupId>org.springframework.boot</groupId>
35.             <artifactId>spring-boot-starter-test</artifactId>
36.             <scope>test</scope>
37.         </dependency>
38.     </dependencies>
40.     <build>
41.         <plugins>
42.             <plugin>
43.                 <groupId>org.springframework.boot</groupId>
44.                 <artifactId>spring-boot-maven-plugin</artifactId>
45.             </plugin>
46.         </plugins>
47.     </build>
48. </project>

more examples here:-
http://docs.spring.io/spring-boot/docs/current/reference/html/cli-using-the-cli.html#cli-init