org.unix4j.command.JoinedCommand Maven / Gradle / Ivy
package org.unix4j.command;
import org.unix4j.context.ExecutionContext;
import org.unix4j.processor.LineProcessor;
/**
* A composite command joining two commands. The output of the
* {@link #getFirst() first} command is joined to the input of the
* {@link #getSecond() second} command.
*/
public class JoinedCommand> implements Command {
private final Command first;
private final Command second;
/**
* Constructor with first and second command in the join.
*
* @param first
* the first command in the join, whose output is joined to the
* input of the second command
* @param second
* the second command in the join, whose input is joined from the
* output of the first command
* @throws NullPointerException
* if any of the command arguments is null
*
*/
public JoinedCommand(Command first, Command second) {
if (first == null) {
throw new NullPointerException("first command cannot be null");
}
if (second == null) {
throw new NullPointerException("second command cannot be null");
}
this.first = first;
this.second = second;
}
public static > JoinedCommand join(Command first, Command second) {
return new JoinedCommand(first, second);
}
/**
* Returns the first command of this joined command
*
* @return the first command in the join
*/
public Command getFirst() {
return first;
}
/**
* Returns the second command of this joined command
*
* @return the second command in the join
*/
public Command getSecond() {
return second;
}
/**
* Returns the joined command names, a string like "echo | grep"
*
* @return the joined command names, a string like "echo | grep"
*/
@Override
public String getName() {
return getFirst().getName() + " | " + getSecond().getName();
}
@Override
public A getArguments(ExecutionContext context) {
return getFirst().getArguments(context);
}
@Override
public Command join(Command next) {
return JoinedCommand.join(getFirst(), getSecond().join(next));
}
/**
* Executes this joined command redirecting the output of the first command
* such that it becomes the input of the second command.
*
* The specified {@code output} object is passed to the second command's
* {@code execute(..)} method. The {@link LineProcessor} returned by the
* second command is passed to the {@code execute(..)} method of the first
* command, with the effect that the first command provides its output to
* the second command as input.
*
* @param context
* context object providing access to the current directory,
* environment variables and other information useful for the
* commands during their execution
* @param output
* the output for the second command
*/
@Override
public LineProcessor execute(ExecutionContext context, LineProcessor output) {
return getFirst().execute(context, getSecond().execute(context, output));
}
/**
* Returns the string representation of this joined command, consisting of
* first and second command including arguments and options.
*
* An example string returned by a joined command is
*
*
* "echo -messages [Hello WORLD] | grep -matchString world -ignoreCase"
*
*
* @return the string representation of this joined command, such as
*
*
* "echo -messages [Hello WORLD] | grep -matchString world -ignoreCase"
*
*/
@Override
public String toString() {
return first + " | " + second;
}
}