Template Pattern is a design pattern in the Java SDK that is widely used in the Java Servlet framework. This pattern is used to define the skeleton of an algorithm in an operation, delaying some steps to subclasses. By using template patterns, subclasses can redefine certain steps in the algorithm without changing the algorithm structure. In the Java Servlet framework, template patterns are applied to the HttpServlet class. HttpServlet is an abstract class that defines the basic operations of a Servlet, such as receiving HTTP requests, processing requests, and sending HTTP responses. Specific Servlet classes can inherit HttpServlet and rewrite some of its methods to implement their own business logic. The following is a complete source code example of a simplified HttpServlet template pattern: ```java public abstract class HttpServlet { public void service(HttpServletRequest request, HttpServletResponse response) { if (request.getMethod().equals("GET")) { doGet(request, response); } else if (request.getMethod().equals("POST")) { doPost(request, response); } else { throw new UnsupportedOperationException("Unsupported HTTP method: " + request.getMethod()); } } public abstract void doGet(HttpServletRequest request, HttpServletResponse response); public abstract void doPost(HttpServletRequest request, HttpServletResponse response); } ``` In the above code, the HttpServlet class is an abstract class. It defines the service method as a Template method pattern, which calls the corresponding doGet or doPost method to process the request according to the HTTP request method. The specific Servlet class needs to inherit HttpServlet and implement doGet and doPost methods to complete its business logic. By using the template pattern of HttpServlet, the basic operations of Servlet can be abstracted, so that specific Servlet classes only need to focus on their own business logic, without dealing with underlying HTTP request and response operations. At the same time, the template pattern also facilitates the extension of the framework, and new functions can be added by inheriting the HttpServlet. Summary: The template pattern is widely used in the HttpServlet class in the Java SDK, providing a skeleton for operations that delay specific implementations to subclasses. By using template patterns, the writing of specific classes can be simplified, so that specific classes only need to focus on their own business logic. At the same time, the template pattern also provides the extensibility of the framework, allowing for the addition of new features through inheritance.

JdbcTemplate is a template pattern implementation class in the Spring framework used to simplify JDBC operations. It encapsulates basic JDBC operations, allowing developers to perform database operations in a more concise manner, avoiding tedious exception handling and resource release. JdbcTemplate provides a series of methods, including querying, updating, batch processing, and other operations. The following is the complete source code of JdbcTemplate: ```java public class JdbcTemplate { private DataSource dataSource; public void setDataSource(DataSource dataSource) { this.dataSource = dataSource; } public void execute(String sql) { Connection conn = null; Statement stmt = null; try { conn = dataSource.getConnection(); stmt = conn.createStatement(); stmt.execute(sql); } catch (SQLException e) { //Exception handling } finally { //Resource release try { if (stmt != null) { stmt.close(); } if (conn != null) { conn.close(); } } catch (SQLException e) { //Exception handling } } } public <T> List<T> query(String sql, RowMapper<T> rowMapper) { Connection conn = null; Statement stmt = null; ResultSet rs = null; try { conn = dataSource.getConnection(); stmt = conn.createStatement(); rs = stmt.executeQuery(sql); List<T> results = new ArrayList<>(); int rowNum = 0; while (rs.next()) { results.add(rowMapper.mapRow(rs, rowNum++)); } return results; } catch (SQLException e) { //Exception handling return null; } finally { //Resource release try { if (rs != null) { rs.close(); } if (stmt != null) { stmt.close(); } if (conn != null) { conn.close(); } } catch (SQLException e) { //Exception handling } } } public int update(String sql) { Connection conn = null; Statement stmt = null; try { conn = dataSource.getConnection(); stmt = conn.createStatement(); return stmt.executeUpdate(sql); } catch (SQLException e) { //Exception handling return -1; } finally { //Resource release try { if (stmt != null) { stmt.close(); } if (conn != null) { conn.close(); } } catch (SQLException e) { //Exception handling } } } } ``` The execute method in JdbcTemplate is used to execute SQL statements, the query method is used to perform query operations and return the result set, and the update method is used to perform update operations and return the number of affected rows. JdbcTemplate uses the template pattern, encapsulating public JDBC operations in Template method pattern, and leaving specific operations to subclasses. Developers only need to inherit JdbcTemplate and implement the RowMapper interface to customize query result mappings. Summary: JdbcTemplate is a template pattern implementation class in the Spring framework that provides simplified database operation methods. It encapsulates the operational details of JDBC, including resource acquisition and release, exception handling, etc. Using JdbcTemplate can improve development efficiency and reduce repetitive code writing.