Reasons to consider spring-boot for your next Spring based application!

Spring-boot  provides a quick way to create a Spring based application. There are some very compelling reasons to consider spring-boot for your next project:

Reason 1 : Simpler Dependency management using spring-boot starter projects.

Consider the effort required to start up a CRUD web application using Spring-boot, assuming that the CRUD is implemented using a h2 database with Spring-Data providing the data access abstraction. The maven pom required for such a project is the following:

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<?xml version="1.0" encoding="UTF-8"?> <project ...       <parent>         <groupId>org.springframework.boot</groupId>         <artifactId>spring-boot-starter-parent</artifactId>         <version>0.5.0.BUILD-SNAPSHOT</version>     </parent>       <dependencies>         <dependency>             <groupId>org.springframework.boot</groupId>             <artifactId>spring-boot-starter-web</artifactId>         </dependency>         <dependency>             <groupId>org.springframework.boot</groupId>             <artifactId>spring-boot-starter-data-jpa</artifactId>         </dependency>   <dependency>    <groupId>org.thymeleaf</groupId>    <artifactId>thymeleaf-spring3</artifactId>   </dependency>   <dependency>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-jetty</artifactId>   </dependency>    <dependency>    <groupId>org.hsqldb</groupId>    <artifactId>hsqldb</artifactId>    <scope>runtime</scope>   </dependency>    <dependency>    <groupId>junit</groupId>    <artifactId>junit</artifactId>    <scope>test</scope>   </dependency>   <dependency>    <groupId>org.hamcrest</groupId>    <artifactId>hamcrest-library</artifactId>    <scope>test</scope>   </dependency>          </dependencies>       <build>         <plugins>             <plugin>                 <groupId>org.springframework.boot</groupId>                 <artifactId>spring-boot-maven-plugin</artifactId>             </plugin>                   </plugins>     </build>   </project>

I have removed a few things for brevity.

Now, compare this to a traditional pom.xml where all the dependencies are typically spelled out:

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.....    <dependencies>   <dependency>    <groupId>junit</groupId>    <artifactId>junit</artifactId>    <version>4.11</version>    <scope>test</scope>   </dependency>   <dependency>    <groupId>org.hamcrest</groupId>    <artifactId>hamcrest-core</artifactId>    <version>1.2.1</version>   </dependency>   <dependency>    <groupId>org.hamcrest</groupId>    <artifactId>hamcrest-library</artifactId>    <version>1.2.1</version>   </dependency>     <dependency>    <groupId>log4j</groupId>    <artifactId>log4j</artifactId>    <version>1.2.16</version>   </dependency>   <dependency>    <groupId>org.slf4j</groupId>    <artifactId>slf4j-api</artifactId>    <version>${slf4j.version}</version>   </dependency>   <dependency>    <groupId>org.slf4j</groupId>    <artifactId>jcl-over-slf4j</artifactId>    <version>${slf4j.version}</version>   </dependency>   <dependency>    <groupId>org.slf4j</groupId>    <artifactId>slf4j-log4j12</artifactId>    <version>${slf4j.version}</version>   </dependency>   <dependency>    <groupId>org.aspectj</groupId>    <artifactId>aspectjrt</artifactId>    <version>${aspectj.version}</version>   </dependency>   <dependency>    <groupId>org.aspectj</groupId>    <artifactId>aspectjweaver</artifactId>    <version>${aspectj.version}</version>   </dependency>         <!-- dependency>             <groupId>javax.servlet</groupId>             <artifactId>servlet-api</artifactId>             <version>2.5</version>             <scope>provided</scope>         </dependency -->         <dependency>             <groupId>javax.servlet</groupId>             <artifactId>javax.servlet-api</artifactId>             <version>3.0.1</version>             <scope>provided</scope>         </dependency>          <dependency>    <groupId>net.sf.flexjson</groupId>    <artifactId>flexjson</artifactId>    <version>2.0</version>   </dependency>   <!-- Spring dependencies -->   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-core</artifactId>    <version>${spring.version}</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-test</artifactId>    <version>${spring.version}</version>    <scope>test</scope>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-context</artifactId>    <version>${spring.version}</version>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-aop</artifactId>    <version>${spring.version}</version>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-aspects</artifactId>    <version>${spring.version}</version>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-tx</artifactId>    <version>${spring.version}</version>   </dependency>   <dependency>    <groupId>com.h2database</groupId>    <artifactId>h2</artifactId>    <version>${h2.version}</version>   </dependency>   <dependency>    <groupId>org.hibernate</groupId>    <artifactId>hibernate-core</artifactId>    <version>${hibernate.version}</version>   </dependency>   <dependency>    <groupId>org.hibernate</groupId>    <artifactId>hibernate-entitymanager</artifactId>    <version>${hibernate.version}</version>    <exclusions>     <exclusion>      <groupId>cglib</groupId>      <artifactId>cglib</artifactId>     </exclusion>     <exclusion>      <groupId>dom4j</groupId>      <artifactId>dom4j</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.hibernate.javax.persistence</groupId>    <artifactId>hibernate-jpa-2.0-api</artifactId>    <version>1.0.0.Final</version>   </dependency>   <dependency>    <groupId>org.hibernate</groupId>    <artifactId>hibernate-validator</artifactId>    <version>4.3.0.Final</version>    <exclusions>     <exclusion>      <groupId>javax.xml.bind</groupId>      <artifactId>jaxb-api</artifactId>     </exclusion>     <exclusion>      <groupId>com.sun.xml.bind</groupId>      <artifactId>jaxb-impl</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>javax.validation</groupId>    <artifactId>validation-api</artifactId>    <version>1.0.0.GA</version>   </dependency>     <dependency>    <groupId>javax.transaction</groupId>    <artifactId>jta</artifactId>    <version>1.1</version>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-jdbc</artifactId>    <version>${spring.version}</version>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-orm</artifactId>    <version>${spring.version}</version>   </dependency>   <dependency>    <groupId>commons-pool</groupId>    <artifactId>commons-pool</artifactId>    <version>1.5.4</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>commons-io</groupId>    <artifactId>commons-io</artifactId>    <version>2.4</version>   </dependency>    <dependency>    <groupId>commons-dbcp</groupId>    <artifactId>commons-dbcp</artifactId>    <version>1.3</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>     <exclusion>      <groupId>commons-pool</groupId>      <artifactId>commons-pool</artifactId>     </exclusion>     <exclusion>      <groupId>xerces</groupId>      <artifactId>xerces</artifactId>     </exclusion>     <exclusion>      <groupId>xerces</groupId>      <artifactId>xercesImpl</artifactId>     </exclusion>     <exclusion>      <groupId>xml-apis</groupId>      <artifactId>xml-apis</artifactId>     </exclusion>    </exclusions>   </dependency>   <!-- Jackson JSON Processor -->   <dependency>       <groupId>com.fasterxml.jackson.core</groupId>       <artifactId>jackson-core</artifactId>       <version>2.2.1</version>   </dependency>   <dependency>       <groupId>com.fasterxml.jackson.core</groupId>       <artifactId>jackson-databind</artifactId>       <version>2.2.1</version>   </dependency>   <dependency>       <groupId>com.fasterxml.jackson.module</groupId>       <artifactId>jackson-module-jaxb-annotations</artifactId>       <version>2.2.1</version>   </dependency>   <dependency>    <groupId>org.apache.tiles</groupId>    <artifactId>tiles-core</artifactId>    <version>2.2.1</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.apache.tiles</groupId>    <artifactId>tiles-jsp</artifactId>    <version>2.2.1</version>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-web</artifactId>    <version>${spring.version}</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.springframework</groupId>    <artifactId>spring-webmvc</artifactId>    <version>${spring.version}</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>commons-digester</groupId>    <artifactId>commons-digester</artifactId>    <version>2.0</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>commons-fileupload</groupId>    <artifactId>commons-fileupload</artifactId>    <version>1.2.1</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.apache.commons</groupId>    <artifactId>commons-lang3</artifactId>    <version>3.1</version>   </dependency>   <dependency>    <groupId>javax.servlet</groupId>    <artifactId>jstl</artifactId>    <version>1.2</version>   </dependency>   <dependency>    <groupId>javax.el</groupId>    <artifactId>el-api</artifactId>    <version>1.0</version>    <scope>provided</scope>   </dependency>   <dependency>    <groupId>joda-time</groupId>    <artifactId>joda-time</artifactId>    <version>1.6</version>   </dependency>   <dependency>    <groupId>javax.servlet.jsp</groupId>    <artifactId>jsp-api</artifactId>    <version>2.1</version>    <scope>provided</scope>   </dependency>   <dependency>    <groupId>org.springframework.security</groupId>    <artifactId>spring-security-core</artifactId>    <version>${spring-security.version}</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.springframework.security</groupId>    <artifactId>spring-security-config</artifactId>    <version>${spring-security.version}</version>    <exclusions>     <exclusion>      <groupId>commons-logging</groupId>      <artifactId>commons-logging</artifactId>     </exclusion>    </exclusions>   </dependency>   <dependency>    <groupId>org.springframework.security</groupId>    <artifactId>spring-security-web</artifactId>    <version>${spring-security.version}</version>   </dependency>   <dependency>    <groupId>org.springframework.security</groupId>    <artifactId>spring-security-taglibs</artifactId>    <version>${spring-security.version}</version>   </dependency>   <dependency>       <groupId>com.googlecode.flyway</groupId>       <artifactId>flyway-core</artifactId>       <version>1.7</version>   </dependency>   <dependency>    <groupId>org.springframework.data</groupId>    <artifactId>spring-data-jpa</artifactId>    <version>${spring-data-jpa.version}</version>   </dependency>             </dependencies> ...

This is indeed a massive improvement in the way Spring specific dependencies are managed.

Reason 2: Quick standalone mode with auto configuration
All that needs to be done to start up a working web application is to run - "mvn spring:boot" and Spring boot does the rest. It provides a way to quickly run the application with an embedded tomcat or jetty container and auto-configures the application based on the libraries available in the classpath without needing any explicit configuration to be provided by the user - for eg. if it finds hsqldb libraries in the classpath it automatically configures a datasource with hsqldb as the embedded database, if it finds thymeleaf jars in the classpath it automatically configures thymeleaf as the templating engine, if it finds hibernate libraries in the classpath then it automatically uses hibernate as the JPA provider. This allows for a progressive enhancement in the development of a working application - Spring boot provides a way for a developer to quickly bootstrap and prototype the application and then slowly replace some of the auto-configured components with more robust alternatives - say a Postgres DB instead of hsqldb etc.

Reason 3: Opinionated Dependencies
Spring boot provides an opinionated and well tested set of dependencies that work well with the Spring ecosystem of projects. for eg. logback with slf4j as the logging dependency, using Servlet 3.0+ apis, Jackson 2.2 for json handling, thymeleaf for web page templating.


Conclusion:
The Spring-boot project is still under heavy development but even in its current state it holds a lot of potential in greatly simplifying application development using Spring umbrella of projects.


Here is a small reference application using Spring-boot - https://github.com/bijukunjummen/spring-boot-mvc-test.git