my spring-boot( Kotlin) Controller don't work that return String - spring-boot

Question

I'm trying to make spring-boot project in Kotlin.
but my Controller don't work..
I want open html file So I prepared upload.html file in resoureces/templates
The following method return String:(
source code is here
#RestController
#RequestMapping("/api")
class RestApiController {
val logger = LoggerFactory.getLogger(RestApiController::class.java!!)
#Autowired
lateinit var parsingservice : ParsingService
#GetMapping("/index")
fun index(response : HttpServletResponse): String {
return "upload"
}
index method is return "upload" and I expected that open upload.html Page in resourecesPackage.
I studied that when method return String in Cotroller spring-boot framework scan that resoureces/templates Path So We can just write htmlfiles name without .html
I searched this problem in this site and I found that java9jdk not support spring-boot yet So I'm reinstalled java8jdk and change project setting.
but that didn't work.
this is my maven setting.
<name>jsonparser</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<kotlin.compiler.incremental>true</kotlin.compiler.incremental>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<kotlin.version>1.2.10</kotlin.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-data-rest</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-stdlib-jre8</artifactId>
<version>${kotlin.version}</version>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-reflect</artifactId>
<version>${kotlin.version}</version>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
<testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<artifactId>kotlin-maven-plugin</artifactId>
<groupId>org.jetbrains.kotlin</groupId>
<version>${kotlin.version}</version>
<configuration>
<compilerPlugins>
<plugin>spring</plugin>
</compilerPlugins>
<jvmTarget>1.8</jvmTarget>
</configuration>
<executions>
<execution>
<id>compile</id>
<phase>compile</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
<execution>
<id>test-compile</id>
<phase>test-compile</phase>
<goals>
<goal>test-compile</goal>
</goals>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-maven-allopen</artifactId>
<version>${kotlin.version}</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
how can I open htmlpage?
thank you for reading
have a nice day:)

Answer 1

You want to return the upload.html template so your controller is not a RestController. Controllers annotated with RestController will just return the response body. This means your get mapping will just return the String "upload".
Replace the RestController annotation with Controller and it will work.