Process HTML file using Thymeleaf in Web based Scopes of Spring and store the processed template as String

Question

I am trying to render an HTML file using thymeleaf and keep the resultant HTML content in a String variable in web-based scopes of Spring so that i can use it l

Answer 1

See update below

When you configure Thymeleaf you should define the template engine and the template resolver otherwise when you autowire defaults are used. If you create an instance every time it is not a good practice. Here a sample configuration:

@Configuration
@EnableWebMvc
public class ThymeleafConfiguration {

    @Bean
    public SpringTemplateEngine templateEngine() {
        SpringTemplateEngine templateEngine = new SpringTemplateEngine();
        templateEngine.setTemplateResolver(thymeleafTemplateResolver());
        return templateEngine;
    }

    @Bean
    public SpringResourceTemplateResolver thymeleafTemplateResolver() {
        SpringResourceTemplateResolver templateResolver 
          = new SpringResourceTemplateResolver();
        templateResolver.setPrefix("/WEB-INF/views/");
        templateResolver.setSuffix(".html");
        templateResolver.setTemplateMode("HTML5");
        return templateResolver;
    }
}

Then if you want to experiment programmatically you can autowire them but the usual flow for serving html pages with thymeleaf is to define the view resolver as well:

@Bean
public ThymeleafViewResolver thymeleafViewResolver() {
    ThymeleafViewResolver viewResolver = new ThymeleafViewResolver();
    viewResolver.setTemplateEngine(templateEngine());
    return viewResolver;
}

With all that in place you can write a controller as:

@Controller
public class MyController {

    @RequestMapping(value = "/test", method = RequestMethod.GET)
    public String test() {
        return "yourTemplateName";
    }
}

Parameters can be passed to the template by using model attributes.

UPDATE 31/07/2018

unfortunately I do not have the time to complete working proof of concept, however I think the below code is enough to show the flow. If you run it and call localhost:8080/test you should be able to see the output html in the console. The pdf generation can be added as a view resolver and/or invoked programmatically, in this example using xhtmlrenderer; I do not have the time to complete it so I commented it out but you can get the point: a service provide the html and pdf generation by autowiring the template engine.

pom.xml

    4.0.0

    com.github.paizo
    html2pdf
    0.0.1-SNAPSHOT
    jar

    html2pdf
    Demo project for Spring Boot

    
        org.springframework.boot
        spring-boot-starter-parent
        2.0.3.RELEASE
         
    

    
        UTF-8
        UTF-8
        1.8
    

    
        
            org.springframework.boot
            spring-boot-starter-thymeleaf
        
        
            org.springframework.boot
            spring-boot-starter-web
        
        
            org.xhtmlrenderer
            flying-saucer-pdf
            9.1.14
        


        
            org.springframework.boot
            spring-boot-starter-test
            test
        
    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    

ThymeleafConfiguration.java

@Configuration
public class ThymeleafConfiguration {

    @Bean
    public SpringTemplateEngine templateEngine() {
        SpringTemplateEngine templateEngine = new SpringTemplateEngine();
        templateEngine.setTemplateResolver(thymeleafTemplateResolver());
        return templateEngine;
    }

    @Bean
    public ClassLoaderTemplateResolver thymeleafTemplateResolver() {
        ClassLoaderTemplateResolver templateResolver = new ClassLoaderTemplateResolver();
        templateResolver.setPrefix("templates/");
        templateResolver.setSuffix(".html");
        templateResolver.setTemplateMode("HTML5");
        return templateResolver;
    }
}

HelloWorldController.java

@Controller
public class HelloWorldController {

    @Autowired
    private Html2PdfService pdfService;

    @GetMapping(path = "/test")
    public String hello() {
        Map parameters = new HashMap();
        parameters.put("name", "Borat");
        System.out.println(pdfService.template2Html("test", parameters));
        return "test";
    }

//    @ResponseBody
//    @GetMapping
//    public ResponseEntity helloPdf() {
//        Map parameters = new HashMap();
//        parameters.put("name", "Borat");
//        pdfService.template2Pdf("test", parameters);
//        String filePath = "PATH_HERE";
//        InputStream inputStream = new FileInputStream(new File(filePath));
//        InputStreamResource inputStreamResource = new InputStreamResource(inputStream);
//        HttpHeaders headers = new HttpHeaders();
//        headers.setContentLength();
//        return new ResponseEntity(inputStreamResource, headers, HttpStatus.OK);
//    }
}

Html2PdfService.java

@Service
public class Html2PdfService {

    @Autowired
    private TemplateEngine templateEngine;

    public OutputStream template2Pdf(String templateName, Map parameters) {
//        OutputStream outputStream = new BufferedOutputStream();
//        IOUtils.copy()
//
//        Context ctx = new Context();
//        String processedHtml = templateEngine.process(templateName, ctx);
//        ITextRenderer renderer = new ITextRenderer();
//        renderer.setDocumentFromString(processedHtml);
//        renderer.layout();
//        renderer.createPDF(os, false);
//        renderer.finishPDF();
        return null;
    }

    public String template2Html(String templateName, Map parameters) {
        Context ctx = new Context();
        ctx.setVariable("name", "pippo");
        String processedHtml = templateEngine.process(templateName, ctx);
        return processedHtml;
    }
}

Html2pdfApplication.java

@SpringBootApplication
public class Html2pdfApplication {

    public static void main(String[] args) {
        SpringApplication.run(Html2pdfApplication.class, args);
    }
}

as a side note if you plan to generate the pdf on the fly and serve it as response in the controller I suggest to use streams and not byte arrays or temp files.