The value of this book, I think, can be summarized in a few points: 1) It allows readers to fully grasp open-source software in the shortest time possible. Content that would normally take half a year or even a year to learn is all covered in this book; 2) Each section is written by authors with deep experience in their respective fields. Beyond simple exposition, it also includes many of the authors' insights, which can help developers avoid taking wrong paths. It must be said that the Electronics Press has chosen a very unique topic. Overall, this book has great reference value, especially for Java application development based on open-source software, covering various aspects such as design, development, operation, maintenance, testing, and project management.