Learn about the common Commons Digest framework and its application scenarios in the common Java library

Common Commons Digester framework and its application scenarios Commons Digester is an open source Java class library for analysis and mapping XML data to Java objects.It provides a simple and flexible way to handle the XML configuration file and convert it into the corresponding Java object structure.Commons Digester is widely used in various scenarios, including configuration parsing, data binding, and conversion from XML to Java objects. The core concept of Commons Digest is a rule, which defines the operation when parsing XML.DIGESTER performs specified operations by named the rules (such as creating new objects, setting attributes, calling methods, etc.), and gradually constructs Java objects when parsing XML.Users can define their own rules and analyze and handle various different XML structures according to their needs. Here are some application scenarios and examples of Commons Digester: 1. Configuration analysis Commons Digester can be used to analyze and load configuration files.Through the rules, it can convert the configuration file into the corresponding Java object structure and use it for use.For example, assuming that there is an XML configuration file to define the data source connection information in the system.You can use Digester to parse the configuration file and map the connection information to an ConnectionConfig object: Digester digester = new Digester(); digester.setValidating(false); digester.addObjectCreate("config/connection", ConnectionConfig.class); digester.addBeanPropertySetter("config/connection/host", "host"); digester.addBeanPropertySetter("config/connection/port", "port"); digester.addBeanPropertySetter("config/connection/username", "username"); digester.addBeanPropertySetter("config/connection/password", "password"); ConnectionConfig config = digester.parse(new File("config.xml")); 2. Data binding Commons Digester can also be used to bind XML data to Java objects.By defining rules, XML data with similar structures can be converted into complex Java object diagrams.This is very useful in the response data of Web services, reading log files, and other scenarios.For example, assuming that there is an XML data that indicates user information, you can use Digerster to convert it into a USER object: Digester digester = new Digester(); digester.addObjectCreate("user", User.class); digester.addBeanPropertySetter("user/id", "id"); digester.addBeanPropertySetter("user/name", "name"); digester.addBeanPropertySetter("user/email", "email"); User user = digester.parse(new File("user.xml")); 3. XML to Java object conversion Commons Digester can also convert complex XML data into Java objects through rules.This can be used to process complex XML data and convert it into an operable Java object.For example, assuming that there is an XML data containing order information, you can use Digerster to convert it to the order object: Digester digester = new Digester(); digester.addObjectCreate("order", Order.class); digester.addBeanPropertySetter("order/id", "id"); digester.addObjectCreate("order/items/item", Item.class); digester.addBeanPropertySetter("order/items/item/name", "name"); digester.addBeanPropertySetter("order/items/item/quantity", "quantity"); digester.addSetNext("order/items/item", "addItem"); Order order = digester.parse(new File("order.xml")); In summary, Commons Digester is a powerful and easy to use Java XML parsing library, which is mainly used to convert XML data into Java objects.It provides flexible rules and mechanisms, and can adapt to different application scenarios, such as configuration parsing, data binding, and conversion from XML to Java objects.By using Commons Digest, developers can process and operate XML data easier to improve the readability and maintenance of the code.