Chapter 333. String Template Component
Available as of Camel version 1.2
The string-template: component allows you to process a message using a String Template. This can be ideal 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-stringtemplate</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>333.1. URI format
string-template:templateName[?options]
Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template.
You can append query options to the URI in the following format, ?option=value&option=value&…
333.2. Options
The String Template component supports 2 options, which are listed below.
| 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 imposes a potential security risk as this opens access to the full power of CamelContext API. | false | boolean |
| allowTemplateFromHeader (producer) | Whether to allow to use resource template from header or not (default false). Enabling this option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. | false | boolean |
The String Template endpoint is configured using URI syntax:
string-template:resourceUri
with the following path and query parameters:
333.2.1. Path Parameters (1 parameters):
| Name | Description | Default | Type |
|---|---|---|---|
| resourceUri | 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 |
333.2.2. Query Parameters (6 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 imposes a potential security risk as this opens access to the full power of CamelContext API. | false | boolean |
| allowTemplateFromHeader (producer) | Whether to allow to use resource template from header or not (default false). Enabling this option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. | false | boolean |
| contentCache (producer) | Sets whether to use resource content cache or not | false | boolean |
| delimiterStart (producer) | The variable start delimiter | < | char |
| delimiterStop (producer) | The variable end delimiter | > | char |
| synchronous (advanced) | Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). | false | boolean |
333.3. Spring Boot Auto-Configuration
The component supports 2 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| camel.component.string-template.enabled | Enable string-template component | true | Boolean |
| camel.component.string-template.resolve-property-placeholders | Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. | true | Boolean |
333.4. Headers
Camel will store a reference to the resource in the message header with key, org.apache.camel.stringtemplate.resource. The Resource is an org.springframework.core.io.Resource object.
333.5. Hot reloading
The string template resource is by default hot-reloadable for both file and classpath resources (expanded jar). If you set contentCache=true, Camel loads the resource only once and hot-reloading is not possible. This scenario can be used in production when the resource never changes.
333.6. StringTemplate Attributes
Since Camel 2.14, you can define the custom context map by setting the message header "CamelStringTemplateVariableMap" just like the below code.
Map<String, Object> variableMap = new HashMap<String, Object>();
Map<String, Object> headersMap = new HashMap<String, Object>();
headersMap.put("name", "Willem");
variableMap.put("headers", headersMap);
variableMap.put("body", "Monday");
variableMap.put("exchange", exchange);
exchange.getIn().setHeader("CamelStringTemplateVariableMap", variableMap);333.7. Samples
For example you could use a string template as follows in order to formulate a response to a message:
from("activemq:My.Queue").
to("string-template:com/acme/MyResponse.tm");333.8. The Email Sample
In this sample we want to use a string template to send an order confirmation email. The email template is laid out in StringTemplate as: This example works for camel 2.11.0. If your camel version is less than 2.11.0, the variables should be started and ended with $.
Dear <headers.lastName>, <headers.firstName> Thanks for the order of <headers.item>. Regards Camel Riders Bookstore <body>
And the java code is as follows:
333.9. See Also
- Configuring Camel
- Component
- Endpoint
- Getting Started
