Although Spring provides integration and support for a huge range of enterprise and other external tools, it intentionally keeps its mandatory dependencies to an absolute minimum: you shouldn’t have to locate and download (even automatically) a large number of jar libraries in order to use Spring for simple use cases. For basic dependency injection there is only one mandatory external dependency, and that is for logging (see below for a more detailed description of logging options).

Next we outline the basic steps needed to configure an application that depends on Spring, first with Maven and then with Gradle and finally using Ivy. In all cases, if anything is unclear, refer to the documentation of your dependency management system, or look at some sample code - Spring itself uses Gradle to manage dependencies when it is building, and our samples mostly use Gradle or Maven.

If you are using Maven for dependency management you don’t even need to supply the logging dependency explicitly. For example, to create an application context and use dependency injection to configure an application, your Maven dependencies will look like this:

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.21.RELEASE</version>
        <scope>runtime</scope>
    </dependency>
</dependencies>

That’s it. Note the scope can be declared as runtime if you don’t need to compile against Spring APIs, which is typically the case for basic dependency injection use cases.

The example above works with the Maven Central repository. To use the Spring Maven repository (e.g. for milestones or developer snapshots), you need to specify the repository location in your Maven configuration. For full releases:

<repositories>
    <repository>
        <id>io.spring.repo.maven.release</id>
        <url>http://repo.spring.io/release/</url>
        <snapshots><enabled>false</enabled></snapshots>
    </repository>
</repositories>

For milestones:

<repositories>
    <repository>
        <id>io.spring.repo.maven.milestone</id>
        <url>http://repo.spring.io/milestone/</url>
        <snapshots><enabled>false</enabled></snapshots>
    </repository>
</repositories>

And for snapshots:

<repositories>
    <repository>
        <id>io.spring.repo.maven.snapshot</id>
        <url>http://repo.spring.io/snapshot/</url>
        <snapshots><enabled>true</enabled></snapshots>
    </repository>
</repositories>

It is possible to accidentally mix different versions of Spring JARs when using Maven. For example, you may find that a third-party library, or another Spring project, pulls in a transitive dependency to an older release. If you forget to explicitly declare a direct dependency yourself, all sorts of unexpected issues can arise.

To overcome such problems Maven supports the concept of a "bill of materials" (BOM) dependency. You can import the spring-framework-bom in your dependencyManagement section to ensure that all spring dependencies (both direct and transitive) are at the same version.

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-framework-bom</artifactId>
            <version>4.3.21.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

An added benefit of using the BOM is that you no longer need to specify the <version> attribute when depending on Spring Framework artifacts:

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
    </dependency>
<dependencies>

To use the Spring repository with the Gradle build system, include the appropriate URL in the repositories section:

repositories {
    mavenCentral()
    // and optionally...
    maven { url "http://repo.spring.io/release" }
}

You can change the repositories URL from /release to /milestone or /snapshot as appropriate. Once a repository has been configured, you can declare dependencies in the usual Gradle way:

dependencies {
    compile("org.springframework:spring-context:4.3.21.RELEASE")
    testCompile("org.springframework:spring-test:4.3.21.RELEASE")
}

If you prefer to use Ivy to manage dependencies then there are similar configuration options.

To configure Ivy to point to the Spring repository add the following resolver to your ivysettings.xml:

<resolvers>
    <ibiblio name="io.spring.repo.maven.release"
            m2compatible="true"
            root="http://repo.spring.io/release/"/>
</resolvers>

You can change the root URL from /release/ to /milestone/ or /snapshot/ as appropriate.

Once configured, you can add dependencies in the usual way. For example (in ivy.xml):

<dependency org="org.springframework"
    name="spring-core" rev="4.3.21.RELEASE" conf="compile->runtime"/>

Although using a build system that supports dependency management is the recommended way to obtain the Spring Framework, it is still possible to download a distribution zip file.

Distribution zips are published to the Spring Maven Repository (this is just for our convenience, you don’t need Maven or any other build system in order to download them).

To download a distribution zip open a web browser to http://repo.spring.io/release/org/springframework/spring and select the appropriate subfolder for the version that you want. Distribution files end -dist.zip, for example spring-framework-{spring-version}-RELEASE-dist.zip. Distributions are also published for milestones and snapshots.

	Note
	Log4j 1.2 is EOL in the meantime. Also, Log4j 2.3 is the last Java 6 compatible release, with newer Log4j 2.x releases requiring Java 7+.

Many people use Log4j as a logging framework for configuration and management purposes. It is efficient and well-established, and in fact it is what we use at runtime when we build Spring. Spring also provides some utilities for configuring and initializing Log4j, so it has an optional compile-time dependency on Log4j in some modules.

To make Log4j 1.2 work with the default JCL dependency (commons-logging) all you need to do is put Log4j on the classpath, and provide it with a configuration file (log4j.properties or log4j.xml in the root of the classpath). So for Maven users this is your dependency declaration:

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.21.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>
</dependencies>

And here’s a sample log4j.properties for logging to the console:

log4j.rootCategory=INFO, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %t %c{2}:%L - %m%n

log4j.category.org.springframework.beans.factory=DEBUG

To use Log4j 2.x with JCL, all you need to do is put Log4j on the classpath and provide it with a configuration file (log4j2.xml, log4j2.properties, or other supported configuration formats). For Maven users, the minimal dependencies needed are:

<dependencies>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.6.2</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-jcl</artifactId>
        <version>2.6.2</version>
    </dependency>
</dependencies>

If you also wish to enable SLF4J to delegate to Log4j, e.g. for other libraries which use SLF4J by default, the following dependency is also needed:

<dependencies>
  <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-slf4j-impl</artifactId>
    <version>2.6.2</version>
  </dependency>
</dependencies>

Here is an example log4j2.xml for logging to the console:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Logger name="org.springframework.beans.factory" level="DEBUG"/>
    <Root level="error">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>

Unfortunately, the runtime discovery algorithm in the standard commons-logging API, while convenient for the end-user, can be problematic. If you’d like to avoid JCL’s standard lookup, there are basically two ways to switch it off:

To exclude commons-logging, add the following to your dependencyManagement section:

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.21.RELEASE</version>
        <exclusions>
            <exclusion>
                <groupId>commons-logging</groupId>
                <artifactId>commons-logging</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

Now this application is currently broken because there is no implementation of the JCL API on the classpath, so to fix it a new one has to be provided. In the next section we show you how to provide an alternative implementation of JCL using SLF4J.

The Simple Logging Facade for Java (SLF4J) is a popular API used by other libraries commonly used with Spring. It is typically used with Logback which is a native implementation of the SLF4J API.

SLF4J provides bindings to many common logging frameworks, including Log4j, and it also does the reverse: bridges between other logging frameworks and itself. So to use SLF4J with Spring you need to replace the commons-logging dependency with the SLF4J-JCL bridge. Once you have done that then logging calls from within Spring will be translated into logging calls to the SLF4J API, so if other libraries in your application use that API, then you have a single place to configure and manage logging.

A common choice might be to bridge Spring to SLF4J, and then provide explicit binding from SLF4J to Log4j. You need to supply several dependencies (and exclude the existing commons-logging): the JCL bridge, the SLF4j binding to Log4j, and the Log4j provider itself. In Maven you would do that like this

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.21.RELEASE</version>
        <exclusions>
            <exclusion>
                <groupId>commons-logging</groupId>
                <artifactId>commons-logging</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>jcl-over-slf4j</artifactId>
        <version>1.7.21</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.7.21</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>
</dependencies>

A more common choice amongst SLF4J users, which uses fewer steps and generates fewer dependencies, is to bind directly to Logback. This removes the extra binding step because Logback implements SLF4J directly, so you only need to depend on just two libraries, namely jcl-over-slf4j and logback):

<dependencies>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>jcl-over-slf4j</artifactId>
        <version>1.7.21</version>
    </dependency>
    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.1.7</version>
    </dependency>
</dependencies>

Commons Logging will delegate to java.util.logging by default, provided that no Log4j is detected on the classpath. So there is no special dependency to set up: just use Spring with no external dependency for log output to java.util.logging, either in a standalone application (with a custom or default JUL setup at the JDK level) or with an application server’s log system (and its system-wide JUL setup).

Spring applications may run on a container that itself provides an implementation of JCL, e.g. IBM’s WebSphere Application Server (WAS). This does not cause issues per se but leads to two different scenarios that need to be understood:

In a "parent first" ClassLoader delegation model (the default on WAS), applications will always pick up the server-provided version of Commons Logging, delegating to the WAS logging subsystem (which is actually based on JUL). An application-provided variant of JCL, whether standard Commons Logging or the JCL-over-SLF4J bridge, will effectively be ignored, along with any locally included log provider.

With a "parent last" delegation model (the default in a regular Servlet container but an explicit configuration option on WAS), an application-provided Commons Logging variant will be picked up, enabling you to set up a locally included log provider, e.g. Log4j or Logback, within your application. In case of no local log provider, regular Commons Logging will delegate to JUL by default, effectively logging to WebSphere’s logging subsystem like in the "parent first" scenario.

All in all, we recommend deploying Spring applications in the "parent last" model since it naturally allows for local providers as well as the server’s log subsystem.