java.lang.ClassNotFoundException: org.springframework.context.event.GenericApplicationListener ----good

Caused by: java.lang.NoClassDefFoundError: org/springframework/context/event/GenericApplicationListener From the above error, application is unable to find the class defined from the jar dependencies. GenericApplicationListener is added from spring version 4.2.

Upgrade your spring version to 4.2 and recheck.

http://*.com/questions/31489947/noclassdeffounderror-genericapplicationlistener-when-switching-from-spring-bo

Spring Boot manages a bunch of dependencies for you and allows you to add them without specifying the version. Spring Boot is obviously based on Spring Framework and uses the latest and greatest so you should avoid at all cost to fix the spring framework version to use yourself.

If you have upgraded to a newer version (to include a bug fix or something) make sure to remove the override before you upgrade Spring Boot as the new version it requires may be incompatible with your override.

If you are using other projects that also provide a dependency management on Spring Framework (such as Spring Cloud) make sure that the dependency management of Spring Boot takes precedence. With Maven, make sure to add the spring-boot-dependencies BOM as the first entry in the <dependenciesManagement> section.

http://*.com/questions/31489947/noclassdeffounderror-genericapplicationlistener-when-switching-from-spring-bo

13.2 Maven

Maven users can inherit from the spring-boot-starter-parent project to obtain sensible defaults. The parent project provides the following features:

• Java 1.6 as the default compiler level.
• UTF-8 source encoding.
• A Dependency Management section, allowing you to omit <version> tags for common dependencies, inherited from the spring-boot-dependencies POM.
• Sensible resource filtering.
• Sensible plugin configuration (exec plugin, surefire, Git commit ID, shade).
• Sensible resource filtering for application.properties and application.yml including profile-specific files (e.g. application-foo.properties andapplication-foo.yml)

On the last point: since the default config files accept Spring style placeholders (${…​}) the Maven filtering is changed to use @..@ placeholders (you can override that with a Maven property resource.delimiter).

13.2.1 Inheriting the starter parent

To configure your project to inherit from the spring-boot-starter-parent simply set the parent:

<!-- Inherit defaults from Spring Boot -->
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.2.RELEASE</version>
</parent>

	You should only need to specify the Spring Boot version number on this dependency. If you import additional starters, you can safely omit the version number.

With that setup, you can also override individual dependencies by overriding a property in your own project. For instance, to upgrade to another Spring Data release train you’d add the following to your pom.xml.

<properties>
    <spring-data-releasetrain.version>Fowler-SR2</spring-data-releasetrain.version>
</properties>

	Check the spring-boot-dependencies pom for a list of supported properties.

13.2.2 Using Spring Boot without the parent POM

Not everyone likes inheriting from the spring-boot-starter-parent POM. You may have your own corporate standard parent that you need to use, or you may just prefer to explicitly declare all your Maven configuration.

If you don’t want to use the spring-boot-starter-parent, you can still keep the benefit of the dependency management (but not the plugin management) by using ascope=import dependency:

<dependencyManagement>
     <dependencies>
        <dependency>
            <!-- Import dependency management from Spring Boot -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>1.4.2.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

That setup does not allow you to override individual dependencies using a property as explained above. To achieve the same result, you’d need to add an entry in thedependencyManagement of your project before the spring-boot-dependencies entry. For instance, to upgrade to another Spring Data release train you’d add the following to your pom.xml.

<dependencyManagement>
    <dependencies>
        <!-- Override Spring Data release train provided by Spring Boot -->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-releasetrain</artifactId>
            <version>Fowler-SR2</version>
            <scope>import</scope>
            <type>pom</type>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>1.4.2.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

	In the example above, we specify a BOM but any dependency type can be overridden that way.

13.2.3 Changing the Java version

The spring-boot-starter-parent chooses fairly conservative Java compatibility. If you want to follow our recommendation and use a later Java version you can add a java.version property:

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

13.2.4 Using the Spring Boot Maven plugin

Spring Boot includes a Maven plugin that can package the project as an executable jar. Add the plugin to your <plugins> section if you want to use it:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

	If you use the Spring Boot starter parent pom, you only need to add the plugin, there is no need for to configure it unless you want to change the settings defined in the parent.