Today when I saw a post, though a bit old, but still quite touched, and I believe many readers have similar years of work experience.
Author of the text in the Internet industry veteran of five years, thought I, "with the existing project experience and work experience," how a person should be regarded as a comparison of the qualifications of the industry, but is in the process of changing jobs The interviewer inquired, Tomcat source, due to understand Chuqian suffered a setback, and decided to pursue research Tomcat source code "shown below." 
After reading the above text, I sentence the interviewer is still quite feelings of.
We do not need skilled workers, we need to have more than ordinary people accumulate knowledge in a certain field, and has a complete set of cognitive thinking and good things capable people.
I read some of the reader comments hold different views, I am inclined to agree with some of these points @ jdon007 of "see below." 
3 to 5 years of working programmer "including me", in fact we are in the stage of a more impetuous, easy to unrealistic expectations, aim too high. . .
This point in time, I think more needs to focus on reality, "the source in the end how much reading frame mean to you?" Rational look at the problem, learn to choose, arrange your time, line up the priority. For example, you can not even usual work can be completed, even responsible for their own business are not familiar with where to spend a lot of time to pull the dead Framework source code, meaning where is it?
It does not mean that you can not read the source code is under the premise that you want to have enough energy. Have not you have not read the source code, it will be unsuccessful interview, if you have a unique perspective on their business, or other skills, the interview is also very easy.
Why interviewers like to ask the source?
I saw a netizen know almost answered in the very image of, for your reference.
Interviews with drivers working for several years almost, most drivers are similar driving level "common framework", the driver of the most important driving skills "tool proficiency" and security awareness "Do not write low-level bug", but it is difficult in the interview measure, then talk to repair it, "the source," at least to be able to see the cause of the problem based on the phenomenon of "positioning bug", although some fault "bug" is not a driver can be resolved, but understand the car, "read the source code." know what the problem is, where to repair "professional advice", small problems can solve yourself "to modify the source code" that he had modified the car, "write the underlying framework" is certainly a professional.
How to stick to it?
I think with the purpose best, for example, you can read the source code of their own income were realized "open payment platform columns on some knowledge," so you will be able to have been read on. Without purpose, you will likely be "three days fishing, two days drying nets."
How to read the source code it?
For reading the source code, although I am not a big cow, but how much or little experience. We all know that "hit the snake fight three inches," read the source code is the same, to seize the key. Take Tomcat thing I read posts mentioned, for example, only three legs of cats, the final analysis is a Servlet container to meet the specification for such a container, it is nothing more than provide services Socket, URL request distribution , package Request / Response, Tomcat only on this basis, made a more detailed treatment, such as the use of design patterns, JMX, Session handling, class loading mechanism and related components, etc., I think the most interesting is that these components "see The following figure".
In general, if sufficient time, it is recommended to read the source code, after all skills are more than body!