OPEN - BATCH-152: Add facility for calling system commands via a Tasklet

added SystemCommandTasklet to samples (example usage in taskletJob)

spring-batch-samples/src/main/java/org/springframework/batch/sample/tasklet/ConfigurableSystemProcessExitCodeMapper.java

@@ -0,0 +1,40 @@
+package org.springframework.batch.sample.tasklet;
+
+import java.util.Map;
+
+import org.springframework.batch.repeat.ExitStatus;
+import org.springframework.util.Assert;
+
+/**
+ * Maps exit codes to {@link org.springframework.batch.repeat.ExitStatus} 
+ * according to injected map. The injected map is required to contain a value 
+ * for 'else' key, this value will be returned if the injected map 
+ * does not contain value for the exit code returned by the system process.
+ * 
+ * @author Robert Kasanicky
+ */
+public class ConfigurableSystemProcessExitCodeMapper implements SystemProcessExitCodeMapper {
+	
+	public static final String ELSE_KEY = "else";
+	
+	private Map mappings;
+
+	public ExitStatus getExitStatus(int exitCode) {
+		ExitStatus exitStatus = (ExitStatus) mappings.get(new Integer(exitCode));
+		if (exitStatus != null) {
+			return exitStatus;
+		} else {
+			return (ExitStatus) mappings.get(ELSE_KEY);
+		}
+	}
+
+	/**
+	 * @param mappings <code>Integer</code> exit code keys to 
+	 * {@link org.springframework.batch.repeat.ExitStatus} values.
+	 */
+	public void setMappings(Map mappings) {
+		Assert.notNull(mappings.get(ELSE_KEY));
+		this.mappings = mappings;
+	}
+
+}

spring-batch-samples/src/main/java/org/springframework/batch/sample/tasklet/SimpleSystemProcessExitCodeMapper.java

@@ -0,0 +1,22 @@
+package org.springframework.batch.sample.tasklet;
+
+import org.springframework.batch.repeat.ExitStatus;
+
+/**
+ * Simple {@link SystemProcessExitCodeMapper} implementation that performs following mapping:
+ * 
+ * 0 	-> ExitStatus.FINISHED
+ * else	-> ExitStatus.FAILED
+ * 
+ * @author Robert Kasanicky
+ */
+public class SimpleSystemProcessExitCodeMapper implements SystemProcessExitCodeMapper {
+	public ExitStatus getExitStatus(int exitCode) {
+		if (exitCode == 0) {
+			return ExitStatus.FINISHED;
+		} else {
+			return ExitStatus.FAILED;
+		}
+	}
+
+}

spring-batch-samples/src/main/java/org/springframework/batch/sample/tasklet/SystemCommandException.java

@@ -0,0 +1,18 @@
+package org.springframework.batch.sample.tasklet;
+
+/**
+ * Exception indicating failed execution of system command.
+ */
+public class SystemCommandException extends RuntimeException {
+	
+	// generated
+	private static final long serialVersionUID = 5139355923336176733L;
+
+	public SystemCommandException(String message) {
+		super(message);
+	}
+	
+	public SystemCommandException(String message, Throwable cause) {
+		super(message, cause);
+	}
+}

spring-batch-samples/src/main/java/org/springframework/batch/sample/tasklet/SystemCommandTasklet.java

@@ -0,0 +1,128 @@
+package org.springframework.batch.sample.tasklet;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.springframework.batch.core.step.tasklet.Tasklet;
+import org.springframework.batch.repeat.ExitStatus;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.util.Assert;
+
+/**
+ * {@link Tasklet} that executes a system command.
+ * 
+ * The system command is executed in a new thread - timeout value is required to
+ * be set, so that the batch job does not hang forever if the external process
+ * hangs.
+ * 
+ * @author Robert Kasanicky
+ */
+public class SystemCommandTasklet implements Tasklet, InitializingBean {
+
+	private String command;
+
+	private String[] environmentParams = null;
+
+	private File workingDirectory = null;
+
+	private SystemProcessExitCodeMapper systemProcessExitCodeMapper = new SimpleSystemProcessExitCodeMapper();
+
+	private long timeout = 0;
+
+	/**
+	 * Execute system command and map its exit code to {@link ExitStatus} using
+	 * {@link SystemProcessExitCodeMapper}.
+	 */
+	public ExitStatus execute() throws Exception {
+		ExecutorThread executorThread = new ExecutorThread();
+		executorThread.start();
+		executorThread.join(timeout);
+
+		if (executorThread.finishedSuccessfully) {
+			return systemProcessExitCodeMapper.getExitStatus(executorThread.exitCode);
+		}
+		else {
+			executorThread.interrupt();
+			throw new SystemCommandException(
+					"Execution of system command failed (did not finish successfully within the timeout)");
+		}
+
+	}
+
+	/**
+	 * @param command command to be executed in a separate system process
+	 */
+	public void setCommand(String command) {
+		this.command = command;
+	}
+
+	/**
+	 * @param envp environment parameter values, inherited from parent process
+	 * when not set (or set to null).
+	 */
+	public void setEnvironmentParams(String[] envp) {
+		this.environmentParams = envp;
+	}
+
+	/**
+	 * @param dir working directory of the spawned process, inherited from
+	 * parent process when not set (or set to null).
+	 */
+	public void setWorkingDirectory(String dir) {
+		if (dir == null) {
+			this.workingDirectory = null;
+			return;
+		}
+		this.workingDirectory = new File(dir);
+		Assert.isTrue(workingDirectory.exists(), "working directory must exist");
+		Assert.isTrue(workingDirectory.isDirectory(), "working directory value must be a directory");
+
+	}
+
+	public void afterPropertiesSet() throws Exception {
+		Assert.hasLength(command, "'command' property value is required");
+		Assert.notNull(systemProcessExitCodeMapper, "SystemProcessExitCodeMapper must be set");
+		Assert.isTrue(timeout > 0, "timeout value must be greater than zero");
+	}
+
+	/**
+	 * @param systemProcessExitCodeMapper maps system process return value to
+	 * <code>ExitStatus</code> returned by Tasklet.
+	 * {@link SimpleSystemProcessExitCodeMapper} is used by default.
+	 */
+	public void setSystemProcessExitCodeMapper(SystemProcessExitCodeMapper systemProcessExitCodeMapper) {
+		this.systemProcessExitCodeMapper = systemProcessExitCodeMapper;
+	}
+
+	/**
+	 * @param timeout upper limit for how long the execution of the external
+	 * program is allowed to last.
+	 */
+	public void setTimeout(long timeout) {
+		this.timeout = timeout;
+	}
+
+	/**
+	 * Thread that executes the system command.
+	 */
+	private class ExecutorThread extends Thread {
+		volatile int exitCode = -1;
+
+		volatile boolean finishedSuccessfully = false;
+
+		public void run() {
+			try {
+				Process process = Runtime.getRuntime().exec(command, environmentParams, workingDirectory);
+				exitCode = process.waitFor();
+				finishedSuccessfully = true;
+			}
+			catch (IOException e) {
+				throw new SystemCommandException("IO error while executing system command", e);
+			}
+			catch (InterruptedException e) {
+				throw new SystemCommandException("Interrupted while executing system command", e);
+			}
+		}
+	}
+
+}

spring-batch-samples/src/main/java/org/springframework/batch/sample/tasklet/SystemProcessExitCodeMapper.java

@@ -0,0 +1,19 @@
+package org.springframework.batch.sample.tasklet;
+
+import org.springframework.batch.repeat.ExitStatus;
+
+/**
+ * Maps the exit code of a system process to ExitStatus value
+ * returned by a system command. Designed for use with the
+ * {@link SystemCommandTasklet}.
+ * 
+ * @author Robert Kasanicky
+ */
+public interface SystemProcessExitCodeMapper {
+	
+	/** 
+	 * @param exitCode exit code returned by the system process
+	 * @return ExitStatus appropriate for the <code>systemExitCode</code> parameter value
+	 */
+	ExitStatus getExitStatus(int exitCode);
+}