Can not resolve WebSecurityConfigurerAdapter class in SpingBoot version 2.0.6 - spring-boot

Question

When I try to write a config class, the WebSecurityConfigurerAdapter class can not be resolved and so does the annotation #EnableWebSecurity.
I reckoned it is caused by the version conflict so I tried to change the version of spring-boot-starter-security. It turns out that the class can not be extended in version 2.0.6 yet it works in 2.0.0.
So is there any substitutions for WebSecurityConfigurerAdapter in 2.0.6?
Here is my pom.xml
<groupId>com.example</groupId>
<artifactId>registertest</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>registertest</name>
<description>Demo login and register for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!--Version 2.0.6 will cause a conflict, we need to modify the version to 1.5.6-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
<version>2.0.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--if you do not want to modify the version above, the following dep is the substitution-->
<!--<dependency>-->
<!--<groupId>org.springframework.security</groupId>-->
<!--<artifactId>spring-security-config</artifactId>-->
<!--<version>4.2.3.RELEASE</version>-->
<!--</dependency>-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</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>
<dependency>
<groupId>net.sourceforge.nekohtml</groupId>
<artifactId>nekohtml</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>

Answer 1

In spring boot 2.0.6, you will still use :
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
If you made a version upgrade, you may have both of them in your .m2 repository and maven does not know which one to use.
Solution: please delete .m2 folder - check its location based on your operating system - and please take notice it is a hidden folder.
Delete version for spring-boot-starter-security and run command mvn clean package to reimport all dependencies.

Answer 2

If you are using parent then not required version to mention in dependencies as it will auto take care of all required compatible version and load..
so just use below without version..
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
</dependency>
Note: WebSecurityConfigurerAdapter is avaibale in 2.0.6 if you would like to extend or you can implement WebSecurityConfigurer.