Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about how to understand the differences between small versions of Tomcat. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

Let's start from here. When debugging in the project, a colleague encountered a cross-domain problem. I remember that Tomcat provided Filter to implement cross-domain (CORS Filter, which was previously written about Tomcat and cross-domain issues). In my impression, starting from Tomcat7, I told people to deploy directly to Tomcat7 and configure CorsFilter in the web.xml of the application.

As a result, it wasn't long before people enthusiastically finished the deployment and found that not only did they not succeed, but also the applications did not start successfully.

What, who's causing trouble?

Pull catalina.jar from the server, and sure enough, there is no corresponding class. So the question is very clear, the version used on the server has not yet provided CorsFilter, so which version should be upgraded to use?

The easiest way is to download the latest version of Tomat 7.x directly. What if you really want to know the lowest version that supports CorsFilter?

On another occasion, a colleague tested a function on the offline server, and the local function was verified normally, but the function did not meet the expectations when it was put offline. Later, a variety of debug analysis found that a feature of Jasper was not supported by the offline server, and it was found that there was a small version difference between the local server and the offline version.

So, let's look at two questions together:

What version is used on the server

In which version of Tomcat provides this feature, and the differences between minor versions

Version determination

How do you determine which version of Tomcat you are currently using?

There is a file under the installation directory of Tomcat: RELEASE-NOTES

Open it and see that at the bottom of the License message, the center of the first screen shows the current Tomcat version.

Apache Tomcat Version 7.0.xx (here is the version number)

Release Notes

In addition to version information, there are also some features provided, changes, and so on.

In addition, under the bin directory of Tomcat, there is a script file for version. Running it, you can learn about the current CATALINA_HOME,CATALINA_BASE,JRE_HOME, Tomcat version, JDK version and other information.

Of course, there is a more common, even do not need to log in to the server, as long as you do not make a special setting for the project error page (error-page, the principle of the error page error-page), then when you request a resource that does not exist, it must display the following error page, the bottom of the page will display the version number of Tomcat.

Differences between versions

If you have determined which version you are currently using, you need to know how to choose the target version, or when you want to know which version of a feature is available:

It's generally called changelog.

Each version of Tomcat will provide a summary of changelog. You can see a section like Apache Tomcat Developers at the bottom of the Docs page, which is for developers. The second item is the Changelog we are interested in.

The changelog page will contain a lot of information, such as

Bug, which can be directly linked to its corresponding bug system, and can view some detailed revision records.

Newly added feature

What improvements have been made?

And these are listed in blocks according to modules, such as the following figure

Divided into Coyote and Catalina two modules, each with a link to the bugId, you can directly jump to the bug system, which contains detailed food bug information, environment description, attachments, as well as some processing suggestions between developers, revise the record. This way of reporting bug is worth learning when we encounter problems and ask for help, and provide complete environmental and abnormal information. How to ask for help-Tomcat officially recommends)

Like the CorsFilter we mentioned earlier, you can find it here so that you can determine the specific version of the implementation to be added.

Similarly, the implementation of a feature can be found in changelog, and if a revision has been made after your current version, you can upgrade directly to the corresponding version, and you can also learn some details of the process.

The above is the editor for you to share how to understand the differences between small versions of Tomcat, if you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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