org.pantsbuild.args4j.ArgfileOptionHandler.java Source code

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Here is the source code for org.pantsbuild.args4j.ArgfileOptionHandler.java

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// Copyright 2015 Pants project contributors (see CONTRIBUTORS.md).
// Licensed under the Apache License, Version 2.0 (see LICENSE).

package org.pantsbuild.args4j;

import java.io.File;
import java.io.IOException;

import com.google.common.base.Charsets;
import com.google.common.io.Files;

import org.kohsuke.args4j.CmdLineException;
import org.kohsuke.args4j.spi.OptionHandler;
import org.kohsuke.args4j.spi.Parameters;

/**
 * <p>
 * An {@code OptionHandler} that can read an option value from an "argfile".
 * </p>
 * An argfile is just a file containing an option's value as its contents.  These can be useful
 * to avoid command-line argument length limits. An argfile is specified on the command-line by
 * prefixing the option argument value with a {@code @}, like so:
 * <pre>-potenially-long-argument=@/path/to/argfile</pre>
 * The path can be relative in which case it is taken as relative to the working directory of the
 * associated java invocation.
 *
 * @param <T> The type of the underlying option value.
 */
public abstract class ArgfileOptionHandler<T> extends OptionHandler<T> {
    private final OptionHandler<T> delegate;

    /**
     * @param delegate The {@code OptionHandler} to delegate final value parsing to.
     */
    protected ArgfileOptionHandler(OptionHandler<T> delegate) {
        super(delegate.owner, delegate.option, delegate.setter);
        this.delegate = delegate;
    }

    @Override
    public int parseArguments(final Parameters params) throws CmdLineException {
        return delegate.parseArguments(new Parameters() {
            @Override
            public String getParameter(int idx) throws CmdLineException {
                String value = params.getParameter(idx);
                if (!value.startsWith("@")) {
                    return value;
                }

                try {
                    return Files.toString(new File(value.substring(1)), Charsets.UTF_8).trim();
                } catch (IOException e) {
                    throw new InvalidCmdLineArgumentException(delegate.option, value,
                            String.format("Failed to read argfile: %s", e.getMessage()));
                }
            }

            @Override
            public int size() {
                return params.size();
            }
        });
    }

    @Override
    public String getDefaultMetaVariable() {
        return delegate.getDefaultMetaVariable();
    }
}