Exec

Since Camel 2.3

Only producer is supported

The Exec component can be used to execute system commands.

Dependencies

Maven users need to add the following dependency to their pom.xml

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-exec</artifactId>
  <version>${camel-version}</version>
</dependency>

where ${camel-version} must be replaced by the actual version of Camel.

URI format

exec://executable[?options]

where executable is the name, or file path, of the system command that will be executed. If executable name is used (e.g. exec:java), the executable must in the system path.

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. 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.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

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

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

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

Component Options

The Exec 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.

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.

boolean

Endpoint Options

The Exec endpoint is configured using URI syntax:

exec:executable

with the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

executable (producer)

Required Sets the executable to be executed. The executable must not be empty or null.

String

Query Parameters (9 parameters)

Name Description Default Type

args (producer)

The arguments may be one or many whitespace-separated tokens.

String

binding (producer)

A reference to a org.apache.commons.exec.ExecBinding in the Registry.

ExecBinding

commandExecutor (producer)

A reference to a org.apache.commons.exec.ExecCommandExecutor in the Registry that customizes the command execution. The default command executor utilizes the commons-exec library, which adds a shutdown hook for every executed command.

ExecCommandExecutor

commandLogLevel (producer)

Logging level to be used for commands during execution. The default value is DEBUG. Possible values are TRACE, DEBUG, INFO, WARN, ERROR or OFF. (Values of ExecCommandLogLevelType enum).

Enum values:

  • TRACE

  • DEBUG

  • INFO

  • WARN

  • ERROR

  • OFF

LoggingLevel

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.

boolean

outFile (producer)

The name of a file, created by the executable, that should be considered as its output. If no outFile is set, the standard output (stdout) of the executable will be used instead.

String

timeout (producer)

The timeout, in milliseconds, after which the executable should be terminated. If execution has not completed within the timeout, the component will send a termination request.

long

useStderrOnEmptyStdout (producer)

A boolean indicating that when stdout is empty, this component will populate the Camel Message Body with stderr. This behavior is disabled (false) by default.

boolean

workingDir (producer)

The directory in which the command should be executed. If null, the working directory of the current process will be used.

String

Message headers

The supported headers are defined in org.apache.camel.component.exec.ExecBinding.

Name Type Message Description

ExecBinding.EXEC_COMMAND_EXECUTABLE

String

in

The name of the system command that will be executed. Overrides executable in the URI.

ExecBinding.EXEC_COMMAND_ARGS

java.util.List<String>

in

Command-line arguments to pass to the executed process. The arguments are used literally - no quoting is applied. Overrides any existing args in the URI.

ExecBinding.EXEC_COMMAND_ARGS

String

in

The arguments of the executable as a Single string where each argument is whitespace separated (see args in URI option). The arguments are used literally, no quoting is applied. Overrides any existing args in the URI.

ExecBinding.EXEC_COMMAND_OUT_FILE

String

in

The name of a file, created by the executable, that should be considered as its output. Overrides any existing outFile in the URI.

ExecBinding.EXEC_COMMAND_TIMEOUT

long

in

The timeout, in milliseconds, after which the executable should be terminated. Overrides any existing timeout in the URI.

ExecBinding.EXEC_COMMAND_WORKING_DIR

String

in

The directory in which the command should be executed. Overrides any existing workingDir in the URI.

ExecBinding.EXEC_EXIT_VALUE

int

out

The value of this header is the exit value of the executable. Non-zero exit values typically indicate abnormal termination. Note that the exit value is OS-dependent.

ExecBinding.EXEC_STDERR

java.io.InputStream

out

The value of this header points to the standard error stream (stderr) of the executable. If no stderr is written, the value is null.

ExecBinding.EXEC_USE_STDERR_ON_EMPTY_STDOUT

boolean

in

Indicates that when stdout is empty, this component will populate the Camel Message Body with stderr. This behavior is disabled (false) by default.

ExecBinding.EXEC_COMMANDS_LOG_LEVEL

String

in

Logging level to be used for commands during execution. The default value is DEBUG. Possible values are TRACE, DEBUG, INFO, WARN, ERROR or OFF (Values of LoggingLevel enum)

Message body

If the Exec component receives an in message body that is convertible to java.io.InputStream, it is used to feed input to the executable via its stdin. After execution, the message body is the result of the execution,- that is, an org.apache.camel.components.exec.ExecResult instance containing the stdout, stderr, exit value, and out file. This component supports the following ExecResult type converters for convenience:

From To

ExecResult

java.io.InputStream

ExecResult

String

ExecResult

byte []

ExecResult

org.w3c.dom.Document

If an out file is specified (in the endpoint via outFile or the message headers via ExecBinding.EXEC_COMMAND_OUT_FILE), converters will return the content of the out file. If no out file is used, then this component will convert the stdout of the process to the target type. For more details, please refer to the usage examples below.

Usage examples

Executing word count (Linux)

The example below executes wc (word count, Linux) to count the words in file /usr/share/dict/words. The word count (output) is written to the standard output stream of wc.

from("direct:exec")
.to("exec:wc?args=--words /usr/share/dict/words")
.process(new Processor() {
     public void process(Exchange exchange) throws Exception {
       // By default, the body is ExecResult instance
       assertIsInstanceOf(ExecResult.class, exchange.getIn().getBody());
       // Use the Camel Exec String type converter to convert the ExecResult to String
       // In this case, the stdout is considered as output
       String wordCountOutput = exchange.getIn().getBody(String.class);
       // do something with the word count
     }
});

Executing java

The example below executes java with 2 arguments: -server and -version, provided that java is in the system path.

from("direct:exec")
.to("exec:java?args=-server -version")

The example below executes java in c:\temp with 3 arguments: -server, -version and the sytem property user.name.

from("direct:exec")
.to("exec:c:/program files/jdk/bin/java?args=-server -version -Duser.name=Camel&workingDir=c:/temp")

Executing Ant scripts

The following example executes Apache Ant (Windows only) with the build file CamelExecBuildFile.xml, provided that ant.bat is in the system path, and that CamelExecBuildFile.xml is in the current directory.

from("direct:exec")
.to("exec:ant.bat?args=-f CamelExecBuildFile.xml")

In the next example, the ant.bat command redirects its output to CamelExecOutFile.txt with -l. The file CamelExecOutFile.txt is used as the out file with outFile=CamelExecOutFile.txt. The example assumes that ant.bat is in the system path, and that CamelExecBuildFile.xml is in the current directory.

from("direct:exec")
.to("exec:ant.bat?args=-f CamelExecBuildFile.xml -l CamelExecOutFile.txt&outFile=CamelExecOutFile.txt")
.process(new Processor() {
     public void process(Exchange exchange) throws Exception {
        InputStream outFile = exchange.getIn().getBody(InputStream.class);
        assertIsInstanceOf(InputStream.class, outFile);
        // do something with the out file here
     }
  });

Executing echo (Windows)

Commands such as echo and dir can be executed only with the command interpreter of the operating system. This example shows how to execute such a command - echo - in Windows.

from("direct:exec").to("exec:cmd?args=/C echo echoString")

Spring Boot Auto-Configuration

When using exec 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-exec-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.exec.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.exec.enabled

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

Boolean

camel.component.exec.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