如何使这个 SwingWorker 代码可测试

考虑这段代码：

public void actionPerformed(ActionEvent e) {
    setEnabled(false);
    new SwingWorker<File, Void>() {

        private String location = url.getText();

        @Override
        protected File doInBackground() throws Exception {
            File file = new File("out.txt");
            Writer writer = null;
            try {
                writer = new FileWriter(file);
                creator.write(location, writer);
            } finally {
                if (writer != null) {
                    writer.close();
                }
            }
            return file;
        }

        @Override
        protected void done() {
            setEnabled(true);
            try {
                File file = get();
                JOptionPane.showMessageDialog(FileInputFrame.this,
                    "File has been retrieved and saved to:\n"
                    + file.getAbsolutePath());
                Desktop.getDesktop().open(file);
            } catch (InterruptedException ex) {
                logger.log(Level.INFO, "Thread interupted, process aborting.", ex);
                Thread.currentThread().interrupt();
            } catch (ExecutionException ex) {
                Throwable cause = ex.getCause() == null ? ex : ex.getCause();
                logger.log(Level.SEVERE, "An exception occurred that was "
                    + "not supposed to happen.", cause);
                JOptionPane.showMessageDialog(FileInputFrame.this, "Error: "
                    + cause.getClass().getSimpleName() + " "
                    + cause.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
            } catch (IOException ex) {
                logger.log(Level.INFO, "Unable to open file for viewing.", ex);
            }
        }
    }.execute();

url是一个 JTextField，“creator”是一个用于写入文件的注入接口（因此该部分正在测试中）。文件写入的位置是有意进行硬编码的，因为这是作为示例。使用 java.util.logging 只是为了避免外部依赖。

您将如何对其进行分块以使其可进行单元测试（包括在需要时放弃 SwingWorker，但随后替换其功能，至少如此处所使用的）。

就我看来，doInBackground 基本上没问题。基本机制是创建一个编写器并关闭它，这几乎太简单而无法测试，真正的工作正在测试中。然而，done 方法存在引用问题，包括它与父类的 actionPerformed 方法的耦合以及协调按钮的启用和禁用。

然而，将其分开并不明显。注入某种 SwingWorkerFactory 会使捕获 GUI 字段的维护变得更加困难（很难看出这会是一个设计改进）。 JOpitonPane 和桌面具有单例的所有“优点”，并且异常处理使得不可能轻松地包装 get。

那么测试这段代码的好解决方案是什么？

恕我直言，这对于匿名类来说很复杂。我的方法是将匿名类重构为如下所示：

public class FileWriterWorker extends SwingWorker<File, Void> {
    private final String location;
    private final Response target;
    private final Object creator;

    public FileWriterWorker(Object creator, String location, Response target) {
        this.creator = creator;
        this.location = location;
        this.target = target;
    }

    @Override
    protected File doInBackground() throws Exception {
        File file = new File("out.txt");
        Writer writer = null;
        try {
            writer = new FileWriter(file);
            creator.write(location, writer);
        }
        finally {
            if (writer != null) {
                writer.close();
            }
        }
        return file;
    }

    @Override
    protected void done() {
        try {
            File file = get();
            target.success(file);
        }
        catch (InterruptedException ex) {
            target.failure(new BackgroundException(ex));
        }
        catch (ExecutionException ex) {
            target.failure(new BackgroundException(ex));
        }
    }

    public interface Response {
        void success(File f);
        void failure(BackgroundException ex);
    }

    public class BackgroundException extends Exception {
        public BackgroundException(Throwable cause) {
            super(cause);
        }
    }
}

这允许独立于 GUI 来测试文件写入功能

然后，actionPerformed变成这样：

public void actionPerformed(ActionEvent e) {
    setEnabled(false);
    Object creator;
    new FileWriterWorker(creator, url.getText(), new FileWriterWorker.Response() {
        @Override
        public void failure(FileWriterWorker.BackgroundException ex) {
            setEnabled(true);
            Throwable bgCause = ex.getCause();
            if (bgCause instanceof InterruptedException) {
                logger.log(Level.INFO, "Thread interupted, process aborting.", bgCause);
                Thread.currentThread().interrupt();
            }
            else if (cause instanceof ExecutionException) {
                Throwable cause = bgCause.getCause() == null ? bgCause : bgCause.getCause();
                logger.log(Level.SEVERE, "An exception occurred that was "
                    + "not supposed to happen.", cause);
                JOptionPane.showMessageDialog(FileInputFrame.this, "Error: "
                    + cause.getClass().getSimpleName() + " "
                    + cause.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
            }
        }

        @Override
        public void success(File f) {
            setEnabled(true);
            JOptionPane.showMessageDialog(FileInputFrame.this,
                "File has been retrieved and saved to:\n"
                + file.getAbsolutePath());
            try {
                Desktop.getDesktop().open(file);
            }
            catch (IOException iOException) {
                logger.log(Level.INFO, "Unable to open file for viewing.", ex);
            }
        }
    }).execute();
}

另外，实例FileWriterWorker.Response可以分配给一个变量并独立于进行测试FileWriterWorker.