Thymeleaf

Since Camel 4.1

Only producer is supported

The Thymeleaf component allows you to process a message using a Thymeleaf template. This can be very powerful when using Templating to generate responses for requests.

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-thymeleaf</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

thymeleaf:templateName[?options]

Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template (e.g.: file://folder/myfile.html).

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

At the component level, you set general and shared configurations that are, then, inherited by the endpoints. It is the highest configuration level.

For example, a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre-configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

You can configure components using:

  • the Component DSL.

  • in a configuration file (application.properties, *.yaml files, etc).

  • directly in the Java code.

Configuring Endpoint Options

You usually spend more time setting up endpoints because they have many options. These options help you customize what you want the endpoint to do. The options are also categorized into whether the endpoint is used as a consumer (from), as a producer (to), or both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders.

Property placeholders provide a few benefits:

  • They help prevent using hardcoded urls, port numbers, sensitive information, and other settings.

  • They allow externalizing the configuration from the code.

  • They help the code to become more flexible and reusable.

The following two sections list all the options, firstly for the component followed by the endpoint.

Component Options

The Thymeleaf component supports 2 options, which are listed below.

Name Description Default Type

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

Endpoint Options

The Thymeleaf endpoint is configured using URI syntax:

thymeleaf:resourceUri

With the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

resourceUri (producer)

Required Path to the resource. You can prefix with: classpath, file, http, ref, or bean. classpath, file and http loads the resource using these protocols (classpath is default). ref will lookup the resource in the registry. bean will call a method on a bean to be used as the resource. For bean you can specify the method name after dot, eg bean:myBean.myMethod.

String

Query Parameters (12 parameters)

Name Description Default Type

allowContextMapAll (producer)

Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so impose a potential security risk as this opens access to the full power of CamelContext API.

false

boolean

cacheable (producer)

Whether templates have to be considered cacheable or not.

Boolean

cacheTimeToLive (producer)

The cache Time To Live for templates, expressed in milliseconds.

Long

checkExistence (producer)

Whether a template resources will be checked for existence before being returned.

Boolean

contentCache (producer)

Sets whether to use resource content cache or not.

false

boolean

templateMode (producer)

The template mode to be applied to templates.

Enum values:

  • HTML

  • XML

  • TEXT

  • JAVASCRIPT

  • CSS

  • RAW

HTML

String

lazyStartProducer (producer (advanced))

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

encoding (advanced)

The character encoding to be used for reading template resources.

String

order (advanced)

The order in which this template will be resolved as part of the resolver chain.

Integer

prefix (advanced)

An optional prefix added to template names to convert them into resource names.

String

resolver (advanced)

The type of resolver to be used by the template engine.

Enum values:

  • CLASS_LOADER

  • DEFAULT

  • FILE

  • STRING

  • URL

  • WEB_APP

CLASS_LOADER

ThymeleafResolverType

suffix (advanced)

An optional suffix added to template names to convert them into resource names.

String

Message Headers

The Thymeleaf component supports 4 message header(s), which is/are listed below:

Name Description Default Type

CamelThymeleafResourceUri (producer)

Constant: THYMELEAF_RESOURCE_URI

The name of the Thymeleaf template.

String

CamelThymeleafTemplate (producer)

Constant: THYMELEAF_TEMPLATE

The content of the Thymeleaf template.

String

CamelThymeleafVariableMap (producer)

Constant: THYMELEAF_VARIABLE_MAP

The value of this header should be a Map with key/values that will be override any existing key with the same name. This can be used to preconfigure common key/values you want to reuse in your Thymeleaf endpoints.

Map

CamelThymeleafServletContext (producer)

Constant: THYMELEAF_SERVLET_CONTEXT

The ServletContext for a web application.

ServletContext

Headers set during the Thymeleaf evaluation are returned to the message and added as headers, thus making it possible to return values from Thymeleaf to the Message.

For example, to set the header value of fruit in the Thymeleaf template fruit-template.html:

$in.setHeader("fruit", "Apple")

The fruit header is now accessible from the message.out.headers.

Usage

Thymeleaf Context

Camel will provide exchange information in the Thymeleaf context (just a Map). The Exchange is transferred as:

key value

exchange

The Exchange itself.

exchange.properties

The Exchange properties.

headers

The headers of the In message.

camelContext

The Camel Context instance.

request

The In message.

in

The In message.

body

The In message body.

out

The Out message (only for InOut message exchange pattern).

response

The Out message (only for InOut message exchange pattern).

You can set up a custom Thymeleaf Context yourself by setting property allowTemplateFromHeader=true and setting the message header CamelThymeleafContext like this

EngineContext engineContext = new EngineContext(variableMap);
exchange.getIn().setHeader("CamelThymeleafContext", engineContext);

Hot reloading

The Thymeleaf template resource is, by default, hot reloadable for both file and classpath resources (expanded jar). If you set contentCache=true, Camel will only load the resource once, and thus hot reloading is not possible. This scenario can be used in production when the resource never changes.

Dynamic templates

Camel provides two headers by which you can define a different resource location for a template or the template content itself. If any of these headers is set, then Camel uses this over the endpoint configured resource. This allows you to provide a dynamic template at runtime.

Header Type Description

CamelThymeleafResourceUri

String

A URI for the template resource to use instead of the endpoint configured.

CamelThymeleafTemplate

String

The template to use instead of the endpoint configured.

Examples

For a simple use case, you could use something like:

from("activemq:My.Queue").
  to("thymeleaf:com/acme/MyResponse.html");

To use a Thymeleaf template to formulate a response to a message for InOut message exchanges (where there is a JMSReplyTo header).

If you want to use InOnly and consume the message and send it to another destination, you could use the following route:

from("activemq:My.Queue")
  .to("thymeleaf:com/acme/MyResponse.html")
  .to("activemq:Another.Queue");

And to use the content cache, e.g., for use in production, where the .html template never changes:

from("activemq:My.Queue")
  .to("thymeleaf:com/acme/MyResponse.html?contentCache=true")
  .to("activemq:Another.Queue");

And a file-based resource:

from("activemq:My.Queue")
  .to("thymeleaf:file://myfolder/MyResponse.html?contentCache=true")
  .to("activemq:Another.Queue");

It’s possible to specify what template the component should use dynamically via a header, so for example:

from("direct:in")
  .setHeader("CamelThymeleafResourceUri").constant("path/to/my/template.html")
  .to("thymeleaf:dummy?allowTemplateFromHeader=true"");

It’s possible to specify a template directly as a header. The component should use it dynamically via a header, so, for example:

from("direct:in")
  .setHeader("CamelThymeleafTemplate").constant("Hi this is a thymeleaf template that can do templating ${body}")
  .to("thymeleaf:dummy?allowTemplateFromHeader=true"");

The Email Example

In this sample, we want to use Thymeleaf templating for an order confirmation email. The email template is laid out in Thymeleaf as:

letter.html
Dear [(${headers.lastName})], [(${headers.firstName})]

Thanks for the order of [(${headers.item})].

Regards Camel Riders Bookstore
[(${body})]

And the java code (from a unit test):

    private Exchange createLetter() {
        Exchange exchange = context.getEndpoint("direct:a").createExchange();
        Message msg = exchange.getIn();
        msg.setHeader("firstName", "Claus");
        msg.setHeader("lastName", "Ibsen");
        msg.setHeader("item", "Camel in Action");
        msg.setBody("PS: Next beer is on me, James");
        return exchange;
    }

    @Test
    public void testThymeleafLetter() throws Exception {
        MockEndpoint mock = getMockEndpoint("mock:result");
        mock.expectedMessageCount(1);
        mock.message(0).body(String.class).contains("Thanks for the order of Camel in Action");

        template.send("direct:a", createLetter());

        mock.assertIsSatisfied();
    }

    @Override
    protected RouteBuilder createRouteBuilder() {
        return new RouteBuilder() {
            public void configure() {
                from("direct:a")
                    .to("thymeleaf:org/apache/camel/component/thymeleaf/letter.txt")
                    .to("mock:result");
            }
        };
    }

Spring Boot Auto-Configuration

When using thymeleaf with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-thymeleaf-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 3 options, which are listed below.

Name Description Default Type

camel.component.thymeleaf.autowired-enabled

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

Boolean

camel.component.thymeleaf.enabled

Whether to enable auto configuration of the thymeleaf component. This is enabled by default.

Boolean

camel.component.thymeleaf.lazy-start-producer

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

Boolean
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