Default value of `server.servlet.session.persistent`

Question

How I see from the Spring Boot documentation the default value of server.servlet.session.persistent option is false but in my application it's true that's strange because I don't modify it explicitly. I guess Spring Security, or Spring Session, or Spring Redis integration turn it into true. May be someone here knows the root of this behaviour?

P.S. I use Spring Boot 2.1.5.

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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>ru.geekmarket</groupId>
    <artifactId>geek-market-ui</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>geek-market-ui</name>
    <description>Geek market e-commerce study project</description>

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

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.thymeleaf.extras</groupId>
            <artifactId>thymeleaf-extras-springsecurity5</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-data-redis</artifactId>
        </dependency>
        <dependency>
            <groupId>io.lettuce</groupId>
            <artifactId>lettuce-core</artifactId>
            <version>5.1.7.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.liquibase</groupId>
            <artifactId>liquibase-core</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>true</filtering>
                <includes>
                    <include>*.properties</include>
                </includes>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>false</filtering>
                <includes>
                    <include>**/static/**/*.*</include>
                    <include>**/templates/**/*.*</include>
                    <include>**/db/**/*.*</include>
                </includes>
            </resource>
        </resources>

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

            <plugin>
                <groupId>org.liquibase</groupId>
                <artifactId>liquibase-maven-plugin</artifactId>
                <version>3.5.5</version>
                <configuration>
                    <propertyFile>${project.build.outputDirectory}/liquibase-maven-plugin.properties</propertyFile>
                    <systemProperties>
                        <user.name>aleks_usharovskii</user.name>
                    </systemProperties>
                    <logging>info</logging>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.liquibase.ext</groupId>
                        <artifactId>liquibase-hibernate5</artifactId>
                        <version>3.6</version>
                    </dependency>
                    <dependency>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-starter-data-jpa</artifactId>
                        <version>2.1.5.RELEASE</version>
                    </dependency>
                    <dependency>
                        <groupId>javax.validation</groupId>
                        <artifactId>validation-api</artifactId>
                        <version>2.0.1.Final</version>
                    </dependency>
                    <dependency>
                        <groupId>org.javassist</groupId>
                        <artifactId>javassist</artifactId>
                        <version>3.24.0-GA</version>
                    </dependency>
                    <dependency>
                        <groupId>org.yaml</groupId>
                        <artifactId>snakeyaml</artifactId>
                        <version>1.12</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

</project>

Answer 1

The property server.servlet.session.persistent is false by default. However, it is overwritten by spring-devtools, which sets it to true (I think due to its restart/hot reload capabilities).

If you do not want session persistence, disable it directly in your application.properties file or in the properties file corresponding to your development profile.

You can check the source code on Github, there are multiple properties set in the Spring Environment by spring-devtools:

static {
    Map<String, Object> properties = new HashMap<>();
    properties.put("spring.thymeleaf.cache", "false");
    properties.put("spring.freemarker.cache", "false");
    properties.put("spring.groovy.template.cache", "false");
    properties.put("spring.mustache.cache", "false");
    properties.put("server.servlet.session.persistent", "true");
    properties.put("spring.h2.console.enabled", "true");
    properties.put("spring.resources.cache.period", "0");
    properties.put("spring.resources.chain.cache", "false");
    properties.put("spring.template.provider.cache", "false");
    properties.put("spring.mvc.log-resolved-exception", "true");
    properties.put("server.error.include-stacktrace", "ALWAYS");
    properties.put("server.servlet.jsp.init-parameters.development", "true");
    properties.put("spring.reactor.debug", "true");
    PROPERTIES = Collections.unmodifiableMap(properties);
}