The role of each jar package in struts2

struts2 jar package description
commons-logging-1.0.4.jar log package
freemarker-2.3.8.jar ognl
-2.6.11.jar
struts2-core-2.0.11.jar core package
xwork-2.0.4.jar xwork depends on The core package, struts2 also depends on



struts2.1.6, at least the following 6 jar packages are required:
struts2-core-2.1.6.jar
freemarker-2.3.13.jar
commons-logging-1.0.4.jar ognl
-2.6. 11.jar
xwork-2.1.2.jar
commons-fileupload-1.2.1.jar

1. commons-beanutils.jar
Commons-Beanutils This is a sub-project in the jakarta commons project. The purpose of this project is to help developers dynamically get/set Java Bean properties, and at the same time solve the trouble of writing getXXX and setXXX every time.

2. commons-digester.jar
Digester was originally just a tool in Jakarta Struts for processing struts-config.xml configuration files. Obviously, converting XML files into corresponding Java objects is a very general function, and this tool should have a wider range of uses, so soon it will be in the Jakarta Commons project (for providing a library of reusable Java components) a place.
Internally, Struts uses Digester from the Jakarta Commons[ASF, Commons] project to parse Struts configuration files. Digester uses the struts-config DTD to validate the format of the document and create the Java objects described by the document. If an XML file contains undocumented elements, or elements are used in an undocumented manner, Digester will not process the file.

3. commons-fileupload.jar
Commons-FileUpload FileUpload enables you to easily add powerful and high-performance file upload capabilities to struts in applications and servlets to upload files.

The validation framework of struts relies on the following two packages:
4. commons-validator.jar
(validation method) and validation rules. Internationalization of validation rules and error messages is supported. Struts uses it to validate the form.

5. jakarta-oro.jar
Commons-EL Commons-Jexl Search Jakarta ORO Jakarta ORO is a set of text processing tools that can provide perl5.0 compatible regular expressions, AWK-like regular expressions, and glob expressions. It also provides functions such as replacement, segmentation, and file name filtering.

6. struts.jar
struts core package.
The other jar packages
7, commons-collections.jar,
extend the standard Java Collection framework, providing additional Map, List and Set implementations and a number of useful utility libraries. More powerful than java.util.*.
8. commons-logging.jar:
One of the Apache Commons packages that includes logging functionality. The package itself contains a Simple Logger, but it is very weak. When running, it will first look for log4j in the CLASSPATH, if there is, use log4j, if not, look for java.util.logging with JDK1.4, if it can't find it, use Simple Logger.
The emergence of commons-logging.jar is a historical regret. At the beginning, Apache tried to persuade Sun to add log4j to JDK1.4. However, the JDK1.4 project team was close to the time to release the JDK1.4 product, so it rejected Apache's Requirements, use your own java.util.logging, the function of this package is far worse than log4j, and the performance is also average.