Chapter 33. Exec
Exec component
Available in Apache Camel 2.3
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 Apache Camel (2.3.0 or higher).
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.
URI options
| Name | Default value | Description |
|---|---|---|
args
|
null
|
The arguments of the executable. The arguments may be one or many whitespace-separated tokens, that can be quoted with
", e.g. args="arg 1" arg2 will use two arguments arg 1 and arg2. To include the quotes use "", e.g. args=""arg 1"" arg2 will use the arguments "arg 1" and arg2.
|
workingDir
|
null
|
The directory in which the command should be executed. If null, the working directory of the current process will be used.
|
timeout
|
Long.MAX_VALUE
|
The timeout, in milliseconds, after which the executable should be terminated. If execution has has not finished within the timeout, the component will send a termination request. |
outFile
|
null
|
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 considered as output.
|
binding
|
a DefaultExecBinding instance
|
A reference to a org.apache.commons.exec.ExecBinding in the Registry.
|
commandExecutor
|
a DefaultCommandExecutor instance
|
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. It adds a shutdown hook for every executed command.
|
useStderrOnEmptyStdout
|
false
|
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.
|
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 the executable in the URI.
|
ExecBinding.EXEC_COMMAND_ARGS
|
java.util.List<String>
|
in
|
The arguments of the executable. The arguments are used literally, no quoting is applied. Overrides existing args in the URI.
|
ExecBinding.EXEC_COMMAND_ARGS
|
String
|
in
|
Camel 2.5: 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 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 output of the executable. Overrides 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.
|
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
|
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 in the standart 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")