In the MyBatis framework, XML ConfigBuilder and XML MapperBuilder are typical applications of the builder pattern. The Builder pattern is a creative design pattern used to separate the construction process of objects from their representations, so that different representations can be created from the same construction process. The builder pattern delegates the construction process of an object to different builders, each responsible for building a portion of the object, and finally the commander calls the builder's methods to assemble the object. This can simplify the process of creating complex objects and improve flexibility. XML ConfigBuilder and XML MapperBuilder are two important builder classes in the MyBatis framework. The XML ConfigBuilder is used to parse the configuration file of MyBatis, which is mybatis config. xml. Its main responsibility is to build the Configuration object. The XML ConfigBuilder delegates the parsing of various sub configurations (such as data source configuration, type alias configuration, mapper configuration, etc.) to the corresponding builders for processing based on the content of the configuration file, and finally integrates these configurations together through the Configuration object. The XML Mapper Builder is used to parse Mapper mapping files, namely *. xml. Its main responsibility is to build the MappedStatement object and register it with the Configuration object. The XML Mapper Builder constructs a MappedStatement object by parsing SQL statements and corresponding parsers in the Mapper mapping file. The following are some original codes for the XML ConfigBuilder and XML MapperBuilder in the MyBatis framework: ```java // XMLConfigBuilder.java public class XMLConfigBuilder extends BaseBuilder { public XMLConfigBuilder(InputStream inputStream, String environment, Properties props) { // ... } public Configuration parse() { // ... parseConfiguration(parser.evalNode("/configuration")); return configuration; } private void parseConfiguration(XNode root) { try { // ... XNode environmentsNode = root.evalNode("environments"); parseEnvironments(environmentsNode); // ... } catch (Exception e) { // ... } } // ... } // XMLMapperBuilder.java public class XMLMapperBuilder extends BaseBuilder { public XMLMapperBuilder(InputStream inputStream, Configuration configuration, String resource, Map<String, XNode> sqlFragments, String namespace) { // ... } public void parse() { try { // ... XNode context = document.getRootElement(); // ... configurationElement(context); } catch (Exception e) { // ... } } private void configurationElement(XNode context) { try { String namespace = context.getStringAttribute("namespace"); // ... BuildStatementFromContext (context. evalNodes ("select | insert | update | delete")); // ... } catch (Exception e) { // ... } } private void buildStatementFromContext(List<XNode> list) { // ... for (XNode context : list) { final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId); // ... statementParser.parseStatementNode(); } } // ... } ``` Summary: Through the builder pattern, the MyBatis framework separates the construction process of objects from their representation, making the construction process flexible and easy to maintain. The XML ConfigBuilder and XML MapperBuilder are used to parse configuration and mapping files, build them into corresponding objects, and register them in the Configuration object of MyBatis. This can achieve unified management and flexible use of configuration files and mapping files. The application of builder pattern in MyBatis framework reflects the Open–closed principle and single responsibility principle in Object-oriented design principles.

Apache POI is an open source framework for reading and writing Microsoft Office format files. It includes a series of APIs that can be used to create, read, and modify files such as Excel, Word, and PowerPoint. In Apache POI, WorkbookBuilder is an implementation of the builder pattern used to create Workbook objects. The Workbook object represents an Excel file and has multiple implementations in POI, such as HSSFWorkbook for manipulating files in. xls format and XSSFWorkbook for manipulating files in. xlsx format. WorkbookBuilder uses a smooth interface, providing a highly readable, easy-to-use, and flexible way to create Workbook objects. It builds the attributes and contents of the Workbook object step by step through a series of Method chaining. The following is the complete source code of WorkbookBuilder: ```java public class WorkbookBuilder { private Workbook workbook; public WorkbookBuilder() { this.workbook = new XSSFWorkbook(); } public WorkbookBuilder createSheet(String sheetName) { workbook.createSheet(sheetName); return this; } public WorkbookBuilder createRow(int sheetIndex, int rowIndex) { workbook.getSheetAt(sheetIndex).createRow(rowIndex); return this; } public WorkbookBuilder createCell(int sheetIndex, int rowIndex, int columnIndex, String value) { Cell cell = workbook.getSheetAt(sheetIndex).getRow(rowIndex).createCell(columnIndex); cell.setCellValue(value); return this; } public Workbook build() { return workbook; } } ``` The example code for creating a Workbook object using WorkbookBuilder is as follows: ```java Workbook workbook = new WorkbookBuilder() .createSheet("Sheet1") .createRow(0, 0) .createCell(0, 0, 0, "Hello World!") .build(); ``` The above code first creates a WorkbookBuilder object, and then continuously calls the createSheet, createRow, and createCell methods through chain calls to create an Excel file containing one cell. Finally, the created Workbook object is obtained through the build method. Summary: The WorkbookBuilder in the Apache POI framework is an implementation of the builder pattern that provides a smooth interface for building Workbook objects. Using WorkbookBuilder can effectively reduce the complexity of code, improve its readability and maintainability. The builder pattern can help developers gradually build complex objects without the need to specify all parameters at once. This makes the construction process more flexible and makes the code easy to extend and modify.