如何使SwingWorker代码可测试 [英] How can this SwingWorker code be made testable

问题描述

考虑以下代码：

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和'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）。写入文件的位置是故意硬编码的，因为这是一个例子。并且java.util.logging仅用于避免外部依赖。

url is a JTextField and 'creator' is an injected interface for writing the file (so that part is under test). The location where the file is written is hard coded on purpose because this is intended as an example. And java.util.logging is used simply to avoid an external dependency.

如何将其组合以使其可单元测试（包括在需要时放弃SwingWorker，但然后替换它的功能，至少在这里使用了。）

How would you chunk this up to make it unit-testable (including abandoning SwingWorker if needed, but then replacing its functionality, at least as used here).

我看待它的方式，doInBackground基本上没问题。基本的机制是创建一个作家并关闭它，这几乎太简单了，无法测试，真正的工作正在测试中。但是，done方法引用有问题，包括它与actionPerformed方法耦合父类并协调启用和禁用按钮。

The way I look at it, the doInBackground is basically alright. The fundamental mechanics are creating a writer and closing it, which is almost too simple to test and the real work is under test. However, the done method is quote problematic, including its coupling with the actionPerformed method the parent class and coordinating the enabling and disabling of the button.

然而，将它分开是不明显。注入某种SwingWorkerFactory会使得捕获GUI字段变得更难维护（很难看出它是如何改进设计的）。 JOpitonPane和桌面具有Singletons的所有优点，异常处理使得无法轻松包装get。

However, pulling that apart is not obvious. Injecting some kind of SwingWorkerFactory makes capturing the GUI fields a lot harder to maintain (it is hard to see how it would be a design improvement). The JOpitonPane and the Desktop have all the "goodness" of Singletons, and exception handling makes it impossible to wrap the get easily.

那么什么是一个很好的解决方案这个代码在测试中？

So what would be a good solution to bring this code under test?

推荐答案

恕我直言，这对于一个匿名的课来说很复杂。我的方法是将匿名类重构为这样：

IMHO, that's complicated for an anonymous class. My approach would be to refactor the anonymous class to something like this:

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);
        }
    }
}

这允许文件写入功能独立于GUI进行测试

That allows the file writing functionality to be tested independent of a GUI

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();
}

此外， FileWriterWorker.Response的实例可以分配给一个变量，并且独立于 FileWriterWorker 进行测试。

Additionally, the instance of FileWriterWorker.Response can be assigned to a variable and tested independent of FileWriterWorker.

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