spring-mvc - 有没有办法让 Spring Thymeleaf 处理字符串模板？

Question

我想写一些类似的东西:

    @Autowired
    private SpringTemplateEngine engine;
....
  // Thymeleaf Context
  WebContext thymeleafContext = new WebContext(request, response, request.getServletContext(), locale);

    // cached html of a thymeleaf template file
    String cachedHtml=....

    // process the cached html
  String html=engine.process(cachedHtml, thymeleafContext);

默认情况下， [process] 方法不能这样做。我可以从文档中了解到我需要一个特殊的模板解析器:

为了执行模板，将使用 process(String, IContext) 方法:
final String result = templateEngine.process("mytemplate", ctx);
“mytemplate”字符串参数是模板名称，它将与 相关联。物理/逻辑位置 模板本身以在模板解析器/s 中配置的方式。

有谁知道如何解决我的问题？

目标是在字符串中缓存 Thymeleaf 模板(文件)，然后处理这些字符串而不是文件。

Answer 1

我们最终使用的解决方案包括一个新的 IResourceResolver带定制 Context而不是自定义 TemplateResolver .我们选择这个是因为我们在大多数情况下仍然想使用类路径扫描，但偶尔会有动态内容。

下面显示了我们是如何做到的:

public class StringAndClassLoaderResourceResolver implements IResourceResolver {


    public StringAndClassLoaderResourceResolver() {
        super();
    }


    public String getName() {
        return getClass().getName().toUpperCase();
    }


    public InputStream getResourceAsStream(final TemplateProcessingParameters params, final String resourceName) {
        Validate.notNull(resourceName, "Resource name cannot be null");
        if( StringContext.class.isAssignableFrom( params.getContext().getClass() ) ){
            String content = ((StringContext)params.getContext()).getContent();
            return IOUtils.toInputStream(content);
        }
        return ClassLoaderUtils.getClassLoader(ClassLoaderResourceResolver.class).getResourceAsStream(resourceName);
    }

    public static class StringContext extends Context{

        private final String content;

        public StringContext(String content) {
            this.content = content;
        }

        public StringContext(String content, Locale locale) {
            super(locale);
            this.content = content;
        }

        public StringContext(String content, Locale locale, Map<String, ?> variables) {
            super(locale, variables);
            this.content = content;
        }

        public String getContent() {
            return content;
        }
    }

测试用例

public class StringAndClassLoaderResourceResolverTest {

    private static SpringTemplateEngine templateEngine;

    @BeforeClass
    public static void setup(){
        TemplateResolver resolver = new TemplateResolver();
        resolver.setResourceResolver(new StringAndClassLoaderResourceResolver());
        resolver.setPrefix("mail/"); // src/test/resources/mail
        resolver.setSuffix(".html");
        resolver.setTemplateMode("LEGACYHTML5");
        resolver.setCharacterEncoding(CharEncoding.UTF_8);
        resolver.setOrder(1);

        templateEngine = new SpringTemplateEngine();
        templateEngine.setTemplateResolver(resolver);
    }

    @Test
    public void testStringResolution() {
        String expected = "<div>dave</div>";
        String input = "<div th:text=\"${userName}\">Some Username Here!</div>";
        IContext context = new StringAndClassLoaderResourceResolver.StringContext(input);
        context.getVariables().put("userName", "dave");
        String actual = templateEngine.process("redundant", context);
        assertEquals(expected, actual);
    }

    @Test
    public void testClasspathResolution(){
        IContext context = new Context();
        context.getVariables().put("message", "Hello Thymeleaf!");
        String actual = templateEngine.process("dummy", context);
        String expected = "<h1>Hello Thymeleaf!</h1>";
        assertEquals(expected, actual);
    }
}

src/main/resources/mail/dummy.html 中的虚拟模板文件

<h1 th:text="${message}">A message will go here!</h1>

注:我们使用 Apache CommonsIO 的 IOUtils 将字符串转换为 InputStream