[[UsingPropertyPlaceholder-UsingPropertyPlaceholder]]
=== Using `PropertyPlaceholder`

*Available as of Camel 2.3*

Camel now provides a new `PropertiesComponent` in `camel-core` which
allows you to use property placeholders when defining Camel
link:endpoint.adoc[Endpoint] URIs. This works much like you would do if
using Spring's `<property-placeholder>` tag. However Spring has a
limitation that prevents third-party frameworks from fully leveraging
Spring property placeholders.

For more details see:
link:faq/how-do-i-use-spring-property-placeholder-with-camel-xml.adoc[How do
I use Spring Property Placeholder with Camel XML].

[[UsingPropertyPlaceholder-BridgingSpringandCamelPropertyPlaceholders]]
===== Bridging Spring and Camel Property Placeholders

From *Camel 2.10*: Spring's property placeholder can be bridged with
Camel's. See below for more details.

The property placeholder is typically used when trying to do any of the
following:

* Lookup or creating endpoints
* Lookup of beans in the link:registry.adoc[Registry]
* Additional supported in Spring XML (see below in examples)
* Using Blueprint `PropertyPlaceholder` with Camel
<<properties-component,Properties>> component
* Using `@PropertyInject` to inject a property in a POJO
* *Camel 2.14.1* Using default value if a property does not exists
* *Camel 2.14.1* Include out of the box functions, to lookup property
values from OS environment variables, JVM system properties, or the
service idiom
* *Camel 2.14.1* Using custom functions, which can be plugged into the
property component

[[UsingPropertyPlaceholder-Format]]
==== Format

The value of a Camel property can be obtained by specifying its key name
within a property placeholder, using the following format: `{{key}}`

For example:
....
{{file.uri}}
....

where `file.uri` is the property key.

Property placeholders can be used to specify parts, or all, of an
endpoint's URI by embedding one or more placeholders in the URI's string
definition.

From *Camel 2.14.1*: you can specify a default value to use if a
property with the key does not exists, e.g., `file.url:/some/path`
where the default value is the text after the colon, e.g.,
`/some/path`.

From *Camel 2.14.1*: do _not_ use a colon in the property key. The colon
character is used as a token separator when providing a default value.

[[UsingPropertyPlaceholder-UsingPropertyResolver]]
==== Using `PropertyResolver`

Camel provides a pluggable mechanism that allows third-parties to
specify their own resolver to use for the lookup of properties.

Camel provides a default implementation
`org.apache.camel.component.properties.DefaultPropertiesResolver`
which is capable of loading properties from the file system, classpath
or link:registry.adoc[Registry]. To indicate which source to use the
location must contain the appropriate prefix.

The list of prefixes is:

[width="100%",cols="50%,50%",options="header",]
|=======================================================================
|Prefix |Description
|`ref:` |Lookup in the link:registry.adoc[Registry.]

|`file:` |Load the from file system.

|`classpath:` |Load from the classpath (this is also the default if no
prefix is provided).

|`blueprint:` |Use a specific OSGi blueprint placeholder service.
|=======================================================================

[[UsingPropertyPlaceholder-DefiningLocation]]
==== Defining Location

The `PropertiesResolver` must be configured with the location(s) to
use when resolving properties. One or more locations can be given.
Specifying multiple locations can be done a couple of ways: using either
a single comma separated string, or an array of strings.

[source,java]
----
pc.setLocation("com/mycompany/myprop.properties,com/mycompany/other.properties");
pc.setLocation(new String[] {"com/mycompany/myprop.properties", "com/mycompany/other.properties"});
----

From *Camel 2.19.0*: you can set which location can be discarded if
missing by setting  `optional=true`, (`false` by default).

Example:

[source,java]
----
pc.setLocations("com/mycompany/override.properties;optional=true,com/mycompany/defaults.properties");
----
 

[[UsingPropertyPlaceholder-UsingSystemandEnvironmentVariablesinLocations]]
==== Using System and Environment Variables in Locations

*Available as of Camel 2.7*

The location now supports using placeholders for JVM system properties
and OS environments variables.

Example:
....
location=file:${karaf.home}/etc/foo.properties
....

In the location above we defined a location using the file scheme using
the JVM system property with key `karaf.home`.

To use an OS environment variable instead you would have to prefix with
`env`:

location=file:${env:APP_HOME}/etc/foo.properties

Where `APP_HOME` is an OS environment variable.

You can have multiple placeholders in the same location, such as:

location=file:${env:APP_HOME}/etc/${prop.name}.properties

[[UsingPropertyPlaceholder-UsingSystemorEnvironmentVariablestoConfigurePropertyPrefixesandSuffixes]]
==== Using System or Environment Variables to Configure Property Prefixes and Suffixes

From *Camel 2.12.5, 2.13.3, 2.14.0*: `propertyPrefix`,
`propertySuffix` configuration properties support the use of
placeholders for de-referencing JVM system properties and OS
environments variables.

Example:

Assume the `PropertiesComponent` is configured with the following
properties file:

[source,java]
----
textdev.endpoint = result1
test.endpoint = result2
----

The same properties file is then referenced from a route definition:


[source,java]
----
PropertiesComponent pc = context.getComponent("properties",
PropertiesComponent.class); pc.setPropertyPrefix("${stage}.");
// ...
context.addRoutes(new RouteBuilder() {
    @Override
    public void configure() throws Exception {
        from("direct:start")
            .to("properties:mock:{{endpoint}}");
    }
});
----

By using the configuration options `propertyPrefix` it's possible to
change the target endpoint simply by changing the value of the system
property `stage` either to `dev` (the message will be routed
to `mock:result1`) or `test` (the message will be routed
to `mock:result2`).

[[UsingPropertyPlaceholder-ConfiguringinJavaDSL]]
==== Configuring in Java DSL

You have to create and register the `PropertiesComponent` under the
name `properties` such as:


[source,java]
----
PropertiesComponent pc = new PropertiesComponent();
pc.setLocation("classpath:com/mycompany/myprop.properties");
context.addComponent("properties", pc);
----

[[UsingPropertyPlaceholder-ConfiguringinSpringXML]]
==== Configuring in Spring XML

Spring XML offers two variations to configure. You can define a spring
bean as a `PropertiesComponent` which resembles the way done in Java
DSL. Or you can use the `<propertyPlaceholder>` tag.

[source,xml]
----
<bean id="properties" class="org.apache.camel.component.properties.PropertiesComponent">
    <property name="location" value="classpath:com/mycompany/myprop.properties"/>
</bean>
----

Using the `<propertyPlaceholder>` tag makes the configuration a bit
more fresh such as:

[source,xml]
----
<camelContext ...>
    <propertyPlaceholder id="properties" location="com/mycompany/myprop.properties"/>
</camelContext>
----

Setting the properties location through the location tag works just fine
but sometime you have a number of resources to take into account and
starting from **Camel 2.19.0** you can set the properties location with
a dedicated `propertiesLocation`:

[source,xml]
----
<camelContext ...>
    <propertyPlaceholder id="myPropertyPlaceholder">
        <propertiesLocation resolver="classpath" path="com/my/company/something/my-properties-1.properties" optional="false"/>
        <propertiesLocation resolver="classpath" path="com/my/company/something/my-properties-2.properties" optional="false"/>
        <propertiesLocation resolver="file" path="${karaf.home}/etc/my-override.properties" optional="true"/>
    </propertyPlaceholder>
</camelContext>
----

===== Specifying the cache option in XML

From *Camel 2.10*: Camel supports specifying a value for the `cache`
option both inside the Spring as well as the Blueprint XML.


[[UsingPropertyPlaceholder-UsingaPropertiesfromthe]]
==== Using a Properties from the link:registry.adoc[Registry]

*Available as of Camel 2.4*

For example in OSGi you may want to expose a service which returns the
properties as a `java.util.Properties` object.

Then you could setup the link:properties.adoc[Properties] component as
follows:

[source,xml]
----
<propertyPlaceholder id="properties" location="ref:myProperties"/>
----

Where `myProperties` is the id to use for lookup in the OSGi registry.
Notice we use the `ref:` prefix to tell Camel that it should lookup
the properties for the link:registry.adoc[Registry].

[[UsingPropertyPlaceholder-ExamplesUsingPropertiesComponent]]
==== Examples Using Properties Component

When using property placeholders in the endpoint URIs you can either use
the `properties:` component or define the placeholders directly in the
URI. We will show example of both cases, starting with the former.

[source,java]
----
// properties
cool.end=mock:result

// route
from("direct:start")
    .to("properties:{{cool.end}}");
----

You can also use placeholders as a part of the endpoint URI:

[source,java]
----
// properties
cool.foo=result

// route
from("direct:start")
    .to("properties:mock:{{cool.foo}}");
----

In the example above the to endpoint will be resolved to
`mock:result`.

You can also have properties with refer to each other such as:


[source,java]
----
// properties
cool.foo=result
cool.concat=mock:{{cool.foo}}

// route
from("direct:start")
    .to("properties:mock:{{cool.concat}}");
----

Notice how `cool.concat` refer to another property.

The `properties:` component also offers you to override and provide a
location in the given URI using the `locations` option:


[source,java]
----
from("direct:start")
    .to("properties:bar.end?locations=com/mycompany/bar.properties");
----

[[UsingPropertyPlaceholder-Examples]]
==== Examples

You can also use property placeholders directly in the endpoint URIs
without having to use `properties:`.


[source,java]
----
// properties
cool.foo=result

// route
from("direct:start")
    .to("mock:{{cool.foo}}");
----

And you can use them in multiple wherever you want them:

[source,java]
----
// properties
cool.start=direct:start
cool.showid=true
cool.result=result

// route
from("{{cool.start}}")
    .to("log:{{cool.start}}?showBodyType=false&showExchangeId={{cool.showid}}")
    .to("mock:{{cool.result}}");
----

You can also your property placeholders when using
link:producertemplate.adoc[ProducerTemplate] for example:


[source,java]
----
template.sendBody("{{cool.start}}", "Hello World");
----


[[UsingPropertyPlaceholder-Examplewithlanguage]]
==== Example with <<simple-language,Simple>> language

The <<simple-language,Simple>> language now also support using property
placeholders, for example in the route below:


[source,java]
----
// properties
cheese.quote=Camel rocks

// route from("direct:start")
    .transform().simple("Hi ${body} do you think ${properties:cheese.quote}?");
----

You can also specify the location in the <<simple-language,Simple>>
language for example:


[source,java]
----
// bar.properties
bar.quote=Beer tastes good

// route
from("direct:start")
    .transform().simple("Hi ${body}. ${properties:com/mycompany/bar.properties:bar.quote}.");
----


[[UsingPropertyPlaceholder-AdditionalPropertyPlaceholderSupportinSpringXML]]
==== Additional Property Placeholder Support in Spring XML

The property placeholders is also supported in many of the Camel Spring
XML tags such as
`<package>`, `<packageScan>`, `<contextScan>`, `<jmxAgent>`, `<endpoint>`, `<routeBuilder>`, `<proxy>`
and the others.

Example using property placeholders in the `<jmxAgent>` tag:

[source,xml]
----
<camelContext xmlns="http://camel.apache.org/schema/spring">
    <propertyPlaceholder id="properties" location="org/apache/camel/spring/jmx.properties"/>
    <!-- we can use propery placeholders when we define the JMX agent -->
    <jmxAgent id="agent" registryPort="{{myjmx.port}}" disabled="{{myjmx.disabled}}"
              usePlatformMBeanServer="{{myjmx.usePlatform}}" createConnector="true"
              statisticsLevel="RoutesOnly" useHostIPAddress="true"/>
    <route id="foo" autoStartup="false">
        <from uri="seda:start"/>
        <to uri="mock:result"/>
    </route>
</camelContext>
----


Example using property placeholders in the attributes of `<camelContext>`:

[source,xml]
----
<camelContext trace="{{foo.trace}}" xmlns="http://camel.apache.org/schema/spring">
    <propertyPlaceholder id="properties" location="org/apache/camel/spring/processor/myprop.properties"/>
    <template id="camelTemplate" defaultEndpoint="{{foo.cool}}"/>
    <route>
        <from uri="direct:start"/>
        <setHeader headerName="{{foo.header}}">
            <simple>${in.body} World!</simple>
        </setHeader>
        <to uri="mock:result"/>
    </route>
</camelContext>
----


[[UsingPropertyPlaceholder-OverridingaPropertySettingUsingaJVMSystemProperty]]
==== Overriding a Property Setting Using a JVM System Property

*Available as of Camel 2.5*

It is possible to override a property value at runtime using a JVM
System property without the need to restart the application to pick up
the change. This may also be accomplished from the command line by
creating a JVM System property of the same name as the property it
replaces with a new value.

Example:


[source,java]
----
PropertiesComponent pc = context.getComponent("properties", PropertiesComponent.class);
pc.setCache(false);
System.setProperty("cool.end", "mock:override");
System.setProperty("cool.result", "override");
context.addRoutes(new RouteBuilder() {
    @Override
    public void configure() throws Exception {
        from("direct:start").to("properties:cool.end");
        from("direct:foo").to("properties:mock:{{cool.result}}");
    }
});
context.start();
getMockEndpoint("mock:override").expectedMessageCount(2);
template.sendBody("direct:start", "Hello World");
template.sendBody("direct:foo", "Hello Foo");
System.clearProperty("cool.end");
System.clearProperty("cool.result");
assertMockEndpointsSatisfied();
----


[[UsingPropertyPlaceholder-UsingPropertyPlaceholdersforAnyKindofAttributeintheXMLDSL]]
==== Using Property Placeholders for Any Kind of Attribute in the XML DSL

*Available as of Camel 2.7*

If you use OSGi Blueprint then this only works from *2.11.1* or *2.10.5*
on.

Previously it was only the `xs:string` type attributes in the XML DSL
that support placeholders. For example often a timeout attribute would
be a `xs:int` type and thus you cannot set a string value as the
placeholder key. This is now possible from Camel 2.7 on using a special
placeholder namespace.

In the example below we use the `prop` prefix for the namespace
`http://camel.apache.org/schema/placeholder` by which we can use the
`prop` prefix in the attributes in the XML DSLs. Notice how we use
that in the link:multicast.adoc[Multicast] to indicate that the option
`stopOnException` should be the value of the placeholder with the key
`stop`.

[source,xml]
----
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:prop="http://camel.apache.org/schema/placeholder"
       xsi:schemaLocation="
           http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
           http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
    <!-- Notice in the declaration above, we have defined the prop prefix as the Camel placeholder namespace -->
    <bean id="damn" class="java.lang.IllegalArgumentException">
        <constructor-arg index="0" value="Damn"/>
    </bean>
    <camelContext xmlns="http://camel.apache.org/schema/spring">
        <propertyPlaceholder id="properties" location="classpath:org/apache/camel/component/properties/myprop.properties"
                             xmlns="http://camel.apache.org/schema/spring"/>
        <route>
            <from uri="direct:start"/>
            <!-- use prop namespace, to define a property placeholder, which maps to option stopOnException={{stop}} -->
            <multicast prop:stopOnException="stop">
            <to uri="mock:a"/>
            <throwException ref="damn"/>
            <to uri="mock:b"/>
            </multicast>
        </route>
    </camelContext>
</beans>
----

In our properties file we have the value defined as:
....
stop=true
....


[[UsingPropertyPlaceholder-UsingPropertyPlaceholderintheJavaDSL]]
==== Using Property Placeholder in the Java DSL

*Available as of Camel 2.7*

Likewise we have added support for defining placeholders in the Java DSL
using the new `placeholder` DSL as shown in the following equivalent
example:

[source,java]
----
from("direct:start")
    // use a property placeholder for the option stopOnException on the Multicast EIP
    // which should have the value of {{stop}} key being looked up in the properties file
    .multicast()
    .placeholder("stopOnException", "stop")
    .to("mock:a")
    .throwException(new IllegalAccessException("Damn"))
    .to("mock:b");
----


[[UsingPropertyPlaceholder-UsingBlueprintPropertyPlaceholderwithCamelRoutes]]
==== Using Blueprint Property Placeholder with Camel Routes

*Available as of Camel 2.7*

Camel supports link:using-osgi-blueprint-with-camel.adoc[Blueprint]
which also offers a property placeholder service. Camel supports
convention over configuration, so all you have to do is to define the
OSGi Blueprint property placeholder in the XML file as shown below:

[source,xml]
----
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:cm="http://aries.apache.org/blueprint/xmlns/blueprint-cm/v1.0.0"
           xsi:schemaLocation="http://www.osgi.org/xmlns/blueprint/v1.0.0 https://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd">
    <!-- OSGI blueprint property placeholder -->
    <cm:property-placeholder id="myblueprint.placeholder" persistent-id="camel.blueprint">
        <!-- list some properties as needed -->
        <cm:default-properties>
            <cm:property name="result" value="mock:result"/>
        </cm:default-properties>
    </cm:property-placeholder>
    <camelContext xmlns="http://camel.apache.org/schema/blueprint">
        <!-- in the route we can use {{ }} placeholders which will lookup in blueprint as Camel
             will auto detect the OSGi blueprint property placeholder and use it -->
        <route>
            <from uri="direct:start"/>
            <to uri="mock:foo"/>
            <to uri="{{result}}"/>
        </route>
    </camelContext>
</blueprint>
----

By default Camel detects and uses OSGi blueprint property placeholder
service. You can disable this by setting the attribute
`useBlueprintPropertyResolver` to false on the `<camelContext>`
definition.

===== About placeholder syntaxes

Notice how we can use the Camel syntax for placeholders `{{ }}` in the
Camel route, which will lookup the value from OSGi blueprint.
The blueprint syntax for placeholders is `${}`. So outside
the `<camelContext>` you must use the `${}` syntax. Where as
inside `<camelContext>` you must use `{{ }}` syntax. OSGi blueprint
allows you to configure the syntax, so you can actually align those if
you want.

You can also explicit refer to a specific OSGi blueprint property
placeholder by its id. For that you need to use the
Camel's `<propertyPlaceholder>` as shown in the example below:

[source,xml]
----
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:cm="http://aries.apache.org/blueprint/xmlns/blueprint-cm/v1.0.0"
           xsi:schemaLocation="http://www.osgi.org/xmlns/blueprint/v1.0.0 https://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd">
    <!-- OSGI blueprint property placeholder -->
    <cm:property-placeholder id="myblueprint.placeholder" persistent-id="camel.blueprint">
        <!-- list some properties as needed -->
        <cm:default-properties>
            <cm:property name="prefix.result" value="mock:result"/>
        </cm:default-properties>
    </cm:property-placeholder>
    <camelContext xmlns="http://camel.apache.org/schema/blueprint">
        <!-- using Camel properties component and refer to the blueprint property placeholder by its id -->
        <propertyPlaceholder id="properties" location="blueprint:myblueprint.placeholder"
                             prefixToken="[[" suffixToken="]]" propertyPrefix="prefix."/>
        <!-- in the route we can use {{ }} placeholders which will lookup in blueprint -->
        <route>
            <from uri="direct:start"/>
            <to uri="mock:foo"/>
            <to uri="[[result]]"/>
        </route>
    </camelContext>
</blueprint>
----

Notice how we use the `blueprint` scheme to refer to the OSGi
blueprint placeholder by its id. This allows you to mix and match, for
example you can also have additional schemes in the location. For
example to load a file from the classpath you can do:

[source,java]
----
location="blueprint:myblueprint.placeholder,classpath:myproperties.properties"
----

Each location is separated by comma.

[[UsingPropertyPlaceholder-OverridingBlueprintPropertyPlaceholdersOutsideCamelContext]]
==== Overriding Blueprint Property Placeholders Outside CamelContext

*Available as of Camel 2.10.4*

When using Blueprint property placeholder in the Blueprint XML file, you
can declare the properties directly in the XML file as shown below:

include::../../../components/camel-test-blueprint/src/test/resources/org/apache/camel/test/blueprint/configadmin-outside.xml[]

Notice that we have a `<bean>` which refers to one of the properties. And in
the Camel route we refer to the other using the `{{ }}` notation.

Now if you want to override these Blueprint properties from an unit
test, you can do this as shown below:

include::../../../components/camel-test-blueprint/src/test/java/org/apache/camel/test/blueprint/ConfigAdminOverridePropertiesOutsideCamelContextTest.java[]

To do this we override and implement the
`useOverridePropertiesWithConfigAdmin` method. We can then put the
properties we want to override on the given props parameter. And the
return value _must_ be the persistence-id of
the `<cm:property-placeholder>` tag, which you define in the blueprint
XML file.

[[UsingPropertyPlaceholder-Usinga.cfgor.propertiesFileForBlueprintPropertyPlaceholders]]
==== Using a `.cfg` or `.properties` File For Blueprint Property Placeholders

*Available as of Camel 2.10.4*

When using Blueprint property placeholder in the Blueprint XML file, you
can declare the properties in a .properties or `.cfg` file. If you use
Apache ServiceMix/Karaf then this container has a convention that it
loads the properties from a file in the etc directory with the naming
`etc/pid.cfg`, where `pid` is the persistence-id.

For example in the blueprint XML file we have the
`persistence-id="stuff"`, which mean it will load the configuration
file as `etc/stuff.cfg`.

include::../../../components/camel-test-blueprint/src/test/resources/org/apache/camel/test/blueprint/configadmin-loadfile.xml[]

Now if you want to unit test this blueprint XML file, then you can override
the `loadConfigAdminConfigurationFile` and tell Camel which file to
load as shown below:

include::../../../components/camel-test-blueprint/src/test/java/org/apache/camel/test/blueprint/ConfigAdminLoadConfigurationFileTest.java[]

Notice that this method requires to return a `String[]` with 2 values. The
1st value is the path for the configuration file to load. The second
value is the persistence-id of the `<cm:property-placeholder>` tag.

The `stuff.cfg` file is just a plain properties file with the property
placeholders such as:

[source,java]
----
## this is a comment
greeting=Bye
----


[[UsingPropertyPlaceholder-Usinga.cfgfileandOverridingPropertiesforBlueprintPropertyPlaceholders]]
==== Using a `.cfg` file and Overriding Properties for Blueprint Property Placeholders

You can do both as well. Here is a complete example. First we have the
Blueprint XML file:

include::../../../components/camel-test-blueprint/src/test/resources/org/apache/camel/test/blueprint/configadmin-loadfileoverride.xml[]

And in the unit test class we do as follows:

include::../../../components/camel-test-blueprint/src/test/java/org/apache/camel/test/blueprint/ConfigAdminLoadConfigurationFileAndOverrideTest.java[]

And the `etc/stuff.cfg` configuration file contains:

[source,java]
----
greeting=Bye
echo=Yay
destination=mock:result
----


[[UsingPropertyPlaceholder-BridgingSpringandCamelPropertyPlaceholders]]
==== Bridging Spring and Camel Property Placeholders

*Available as of Camel 2.10*

The Spring Framework does not allow third-party frameworks such as
Apache Camel to seamless hook into the Spring property placeholder
mechanism. However you can easily bridge Spring and Camel by declaring a
Spring bean with the type
`org.apache.camel.spring.spi.BridgePropertyPlaceholderConfigurer`,
which is a Spring
`org.springframework.beans.factory.config.PropertyPlaceholderConfigurer`
type.

To bridge Spring and Camel you must define a single bean as shown below:

include::../../../components/camel-spring/src/test/resources/org/apache/camel/component/properties/CamelSpringPropertyPlaceholderConfigurerTest.xml[]

You *must not* use the spring `<context:property-placeholder>` namespace
at the same time; this is not possible.

After declaring this bean, you can define property placeholders using
both the Spring style, and the Camel style within the `<camelContext>`
tag as shown below:

include::../../../components/camel-spring/src/test/resources/org/apache/camel/component/properties/CamelSpringPropertyPlaceholderConfigurerTest.xml[]

Notice how the hello bean is using pure Spring property placeholders using
the `${}` notation. And in the Camel routes we use the Camel
placeholder notation with `{{ }}`.

[[UsingPropertyPlaceholder-ClashingSpringPropertyPlaceholderswithCamelsLanguage]]
==== Clashing Spring Property Placeholders with Camels <<simple-language,Simple>> Language

Take notice when using Spring bridging placeholder then the
spring `${}` syntax clashes with the <<simple-language,Simple>> in
Camel, and therefore take care.

Example:

[source,xml]
----
<setHeader headerName="Exchange.FILE_NAME">
    <simple>{{file.rootdir}}/${in.header.CamelFileName}</simple>
</setHeader>
----

clashes with Spring property placeholders, and you should
use `$simple{}` to indicate using the <<simple-language,Simple>>
language in Camel.


[source,xml]
----
<setHeader headerName="Exchange.FILE_NAME">
    <simple>{{file.rootdir}}/$simple{in.header.CamelFileName}</simple>
</setHeader>
----

An alternative is to configure the `PropertyPlaceholderConfigurer`
with `ignoreUnresolvablePlaceholders` option to `true`.

[[UsingPropertyPlaceholder-OverridingPropertiesfromCamelTestKit]]
==== Overriding Properties from Camel Test Kit

*Available as of Camel 2.10*

When link:testing.adoc[Testing] with Camel and using the
link:properties.adoc[Properties] component, you may want to be able to
provide the properties to be used from directly within the unit test
source code. This is now possible from Camel 2.10, as the Camel test
kits, e.g., `CamelTestSupport` class offers the following methods

* `useOverridePropertiesWithPropertiesComponent`
* `ignoreMissingLocationWithPropertiesComponent`

So for example in your unit test classes, you can override the
`useOverridePropertiesWithPropertiesComponent` method and return a
`java.util.Properties` that contains the properties which should be
preferred to be used.

include::../../../components/camel-test-blueprint/src/test/java/org/apache/camel/test/blueprint/ConfigAdminOverridePropertiesTest.java[]

This can be done from any of the Camel Test kits, such as `camel-test`,
`camel-test-spring` and `camel-test-blueprint`.

The `ignoreMissingLocationWithPropertiesComponent` can be used to
instruct Camel to ignore any locations which was not discoverable. For
example if you run the unit test, in an environment that does not have
access to the location of the properties.


[[UsingPropertyPlaceholder-UsingPropertyInject]]
==== Using `@PropertyInject`

*Available as of Camel 2.12*

Camel allows to inject property placeholders in POJOs using
the `@PropertyInject` annotation which can be set on fields and setter
methods. For example you can use that with `RouteBuilder` classes,
such as shown below:

[source,java]
----
public class MyRouteBuilder extends RouteBuilder {

    @PropertyInject("hello")
    private String greeting;

    @Override
    public void configure() throws Exception {
        from("direct:start")
            .transform().constant(greeting)
            .to("{{result}}");
    }
}
----

Notice we have annotated the greeting field with `@PropertyInject` and
define it to use the key `hello`. Camel will then lookup the property
with this key and inject its value, converted to a String type.

You can also use multiple placeholders and text in the key, for example
we can do:

[source,java]
----
@PropertyInject("Hello {{name}} how are you?")
private String greeting;
----

This will lookup the placeholder with they key `name`.

You can also add a default value if the key does not exists, such as:

[source,java]
----
@PropertyInject(value = "myTimeout", defaultValue = "5000")
private int timeout;
----


[[UsingPropertyPlaceholder-UsingOutoftheBoxFunctions]]
==== Using Out of the Box Functions

*Available as of Camel 2.14.1*

The link:properties.adoc[Properties] component includes the following
functions out of the box

* `env` - A function to lookup the property from OS environment
variables.
* `sys` - A function to lookup the property from Java JVM system
properties.
* `service` - A function to lookup the property from OS environment
variables using the service naming idiom.
* `service.host` - **Camel 2.16.1: **A function to lookup the
property from OS environment variables using the service naming idiom
returning the hostname part only.
* `service.port` - **Camel 2.16.1: **A function to lookup the
property from OS environment variables using the service naming idiom
returning the port part only.

As you can see these functions is intended to make it easy to lookup
values from the environment. As they are provided out of the box, they
can easily be used as shown below:

[source,xml]
----
<camelContext xmlns="http://camel.apache.org/schema/blueprint">
    <route>
        <from uri="direct:start"/>
        <to uri="{{env:SOMENAME}}"/>
        <to uri="{{sys:MyJvmPropertyName}}"/>
    </route>
</camelContext>
----

You can use default values as well, so if the property does not exists,
you can define a default value as shown below, where the default value
is a `log:foo` and `log:bar` value.


[source,xml]
----
<camelContext xmlns="http://camel.apache.org/schema/blueprint">
    <route>
        <from uri="direct:start"/>
        <to uri="{{env:SOMENAME:log:foo}}"/>
        <to uri="{{sys:MyJvmPropertyName:log:bar}}"/>
    </route>
</camelContext>
----

The service function is for looking up a service which is defined using
OS environment variables using the service naming idiom, to refer to a
service location using `hostname : port`

* __NAME___SERVICE_HOST
* __NAME___SERVICE_PORT

in other words the service uses `_SERVICE_HOST` and `_SERVICE_PORT`
as prefix. So if the service is named `FOO`, then the OS environment
variables should be set as

export $FOO_SERVICE_HOST=myserver export $FOO_SERVICE_PORT=8888

For example if the `FOO` service a remote HTTP service, then we can
refer to the service in the Camel endpoint URI, and use
the link:http.adoc[HTTP] component to make the HTTP call:

[source,xml]
----
<camelContext xmlns="http://camel.apache.org/schema/blueprint">
    <route>
        <from uri="direct:start"/>
        <to uri="http://{{service:FOO}}/myapp"/>
    </route>
</camelContext>
----

And we can use default values if the service has not been defined, for
example to call a service on localhost, maybe for unit testing etc:

[source,xml]
----
<camelContext xmlns="http://camel.apache.org/schema/blueprint">
    <route>
        <from uri="direct:start"/>
        <to uri="http://{{service:FOO:localhost:8080}}/myapp"/>
    </route>
</camelContext>
----

[[UsingPropertyPlaceholder-UsingCustomFunctions]]
==== Using Custom Functions

*Available as of Camel 2.14.1*

The link:properties.adoc[Properties] component allow to plugin 3rd party
functions which can be used during parsing of the property placeholders.
These functions are then able to do custom logic to resolve the
placeholders, such as looking up in databases, do custom computations,
or whatnot. The name of the function becomes the prefix used in the
placeholder. This is best illustrated in the example code below

[source,xml]
----
<bean id="beerFunction" class="MyBeerFunction"/>
<camelContext xmlns="http://camel.apache.org/schema/blueprint">
    <propertyPlaceholder id="properties" location="none" ignoreMissingLocation="true">
        <propertiesFunction ref="beerFunction"/>
    </propertyPlaceholder>
    <route>
        <from uri="direct:start"/>
        <to uri="{{beer:FOO}}"/>
        <to uri="{{beer:BAR}}"/>
    </route>
</camelContext>
----

Here we have a Camel XML route where we have defined
the `<propertyPlaceholder>` to use a custom function, which we refer
to be the bean id - e.g., the `beerFunction`. As the beer function
uses `beer` as its name, then the placeholder syntax can trigger the
beer function by starting with `beer:value`.

The implementation of the function is only two methods as shown below:

[source,java]
----
public static final class MyBeerFunction implements PropertiesFunction {
    @Override
    public String getName() {
        return "beer";
    }
    @Override
    public String apply(String remainder) {
        return "mock:" + remainder.toLowerCase();
    }
}
----

The function must implement
the `org.apache.camel.component.properties.PropertiesFunction`
interface. The method `getName` is  the name of the function, e.g.,
`beer`. And the `apply` method is where we implement the custom
logic to do. As the sample code is from an unit test, it just returns a
value to refer to a mock endpoint.

To register a custom function from Java code is as shown below:

[source,java]
----
PropertiesComponent pc = context.getComponent("properties", PropertiesComponent.class);
pc.addFunction(new MyBeerFunction());
----


[[UsingPropertyPlaceholder-SeeAlso]]
==== See Also

* <<properties-component,Properties>> component
