Spring Boot tutorial

Thymeleaf templates

Thymeleaf is one of the template engines that has built-in support in Spring Boot. Read more about Thymeleaf syntax.

Add dependency to your project

dependencies {
...
implementation("org.springframework.boot:spring-boot-starter-thymeleaf")
}

Set default location for your templates in property file

# resource/application.properties
spring.thymeleaf.prefix=classpath:/templates

Suppose we have an article.html template in our templates directory. Then we can us it in controller 

@GetMapping("/articles/{idArticle}")
fun showPage(@PathVariable idArticle: Long)
    = ModelAndView("/article").apply {
        // add objects, that will be passed to the template
        addObject("articleModel", srv.loadData(idArticle))
   }

If you run your Spring Boot application as a jar, you must add / before the template name.

multiple resolvers

You can add multiple resolvers for example for the different template locations. Thymeleaf has built-in resolvers, that can load external templates:

  • ClassLoaderTemplateResolver - resolves templates inside classpath
  • FileTemplateResolver - resolves template on file system
  • ServletContextTemplateResolver - can be used inside your servlet
  • UrlTemplateResource - resolves template from url;
  • SpringResourceTemplateResolver - resolves templates using Spring's Resource Resolution mechanism
@Configuration
class ThymeleafCfg {

    @Bean
    fun fileTemplateResolver() = FileTemplateResolver().apply {
        prefix = "./resources/tpl"
        suffix = ".html"
        
        // set patterns for the template name 
        // resolvablePatterns = setOf("tpl-*") 
        
        templateMode = TemplateMode.HTML 
        characterEncoding = "UTF-8"
        order = 1 // order should start with 1
        
        // allows to pass control to the next resolver in chain
        checkExistence = true 
        
        name = "file-resolver" // optionally
        
        cacheTTLMs = 30 * 60 * 1000 // cache template 30 min
        
        // Set to false if you want templates to
        // be automatically updated when modified.
        // set to false, if you want reload
        isCacheable = false // default true
    }

    // this is same as we set in property file
    // spring.thymeleaf.prefix=classpath:/templates
    @Bean
    fun defaultTemplateResolver() = ClassLoaderTemplateResolver().apply {
        prefix = "/templates" // classpath: will be prepend
        suffix = ".html"
        templateMode = TemplateMode.HTML
        characterEncoding = "UTF-8"
        order = 2 // Order should start with 1
        checkExistence = false
    }
}

custom resolvers

You can define own resolver by implementing the ITemplateResolver interface or extend existing.

For example you can extend StringTemplateResolver class to create resolver that load template from database.

// Entity for template
@Document
class PageTemplate {

    @Id
    var name: String = "" 
    var content: String=""
}
// Resolver that loads Thymeleaf template from mongoDB. 
// You can adapt it for any db.
@Component
class DbTemplateResolver : StringTemplateResolver() {

    @Autowired
    lateinit var pageTemplateRepo: PageTemplateRepository

    init {
       // setup your default configuration
       isCacheable = false
    }


    // try load template by name
    // if found then call super method and pass content of template
    // if not found then return null
    override fun computeTemplateResource(
        configuration: IEngineConfiguration?,
        ownerTemplate: String?,
        template: String?, // template name
        templateResolutionAttributes: MutableMap<String, Any>?
    ): ITemplateResource? = pageTemplateRepo
        .findByIdOrNull(
            if ((template ?: "default-template").trim().isEmpty()) {
                "default-template"
            } else template!!
        )
        ?.let { pageTemplate ->
            super.computeTemplateResource(
                configuration, ownerTemplate,
                pageTemplate.content, templateResolutionAttributes
            )
        }
}