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

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 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.

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 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 (10 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

DEBUG

LoggingLevel

exitValues (producer)

The exit values of successful executions. If the process exits with another value, an exception is raised. Comma-separated list of exit values. And empty list (the default) sets no expected exit values and disables the check.

String

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.

false

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

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

Message Headers

The Exec component supports 10 message header(s), which is/are listed below:

Name Description Default Type

CamelExecCommandExecutable (in)

Constant: EXEC_COMMAND_EXECUTABLE

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

String

CamelExecCommandArgs (in)

Constant: EXEC_COMMAND_ARGS

Command-line argument(s) to pass to the executed process. The argument(s) is/are used literally - no quoting is applied. Overrides any existing args in the URI.

List or String

CamelExecCommandOutFile (in)

Constant: EXEC_COMMAND_OUT_FILE

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

String

CamelExecCommandWorkingDir (in)

Constant: EXEC_COMMAND_WORKING_DIR

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

String

CamelExecCommandTimeout (in)

Constant: EXEC_COMMAND_TIMEOUT

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

long

CamelExecExitValues (in)

Constant: EXEC_COMMAND_EXIT_VALUES

The exit values for successful execution of the process. Overrides any existing exitValues in the URI.

String

CamelExecStderr (out)

Constant: EXEC_STDERR

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

InputStream

CamelExecExitValue (out)

Constant: EXEC_EXIT_VALUE

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.

int

CamelExecUseStderrOnEmptyStdout (in)

Constant: EXEC_USE_STDERR_ON_EMPTY_STDOUT

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

boolean

CamelExecCommandLogLevel (in)

Constant: EXEC_COMMAND_LOG_LEVEL

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).

String

Usage

Message body

If the component receives an in message body that is convertible to java.io.InputStream, it is used to feed input to the executable via its standard input (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 the 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), the 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.

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 two arguments: -server and -version, if java is in the system path.

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

The example below executes java in c:\temp with three arguments: -server, -version and the system 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
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