javaweb使用Thymeleaf 最凝练的CRUD项目-上

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://192.168.198.100:3306/view-demo
username=root
password=atguigu
initialSize=10
maxActive=20
maxWait=10000

public class JDBCUtil {

    // 将数据源对象设置为静态属性，保证大对象的单一实例
    private static DataSource dataSource;

    static {

        // 1.创建一个用于存储外部属性文件信息的Properties对象
        Properties properties = new Properties();

        // 2.使用当前类的类加载器加载外部属性文件：jdbc.properties
        InputStream inputStream = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");

        try {

            // 3.将外部属性文件jdbc.properties中的数据加载到properties对象中
            properties.load(inputStream);

            // 4.创建数据源对象
            dataSource = DruidDataSourceFactory.createDataSource(properties);

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    /**
     * 从数据源中获取数据库连接
     * @return 数据库连接对象
     */
    public static Connection getConnection() {

        Connection connection = null;

        try {
            connection = dataSource.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();

            throw new RuntimeException(e);
        }

        return connection;

    }

    /**
     * 释放数据库连接
     * @param connection 要执行释放操作的连接对象
     */
    public static void releaseConnection(Connection connection) {

        if (connection != null) {

            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();

                throw new RuntimeException(e);
            }

        }

    }
    
}

public class DemoTest {

    @Test
    public void testConnection() {
        Connection connection = JDBCUtil.getConnection();
        System.out.println("connection = " + connection);
    }

}

public class BaseDao<T> {

    private QueryRunner queryRunner = new QueryRunner();

    /**
     * 通用的增删改方法
     * @param sql
     * @param param
     * @return
     */
    public int update(String sql, Object ... param) {

        Connection connection = JDBCUtil.getConnection();

        int count = 0;
        try {
            count = queryRunner.update(connection, sql, param);
        } catch (SQLException e) {
            e.printStackTrace();

            throw new RuntimeException(e);

        } finally {
            
            // 关闭数据库连接
            JDBCUtil.releaseConnection(connection);
            
        }

        return count;
    }

    /**
     * 查询单个对象的通用方法
     * @param clazz
     * @param sql
     * @param param
     * @return
     */
    public T getBean(Class<T> clazz, String sql, Object ... param) {

        Connection connection = JDBCUtil.getConnection();

        T bean = null;
        try {
            bean = queryRunner.query(connection, sql, new BeanHandler<>(clazz), param);
        } catch (SQLException e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        } finally {
            
            // 关闭数据库连接
            JDBCUtil.releaseConnection(connection);
            
        }

        return bean;
    }

    /**
     * 查询集合对象的通用方法
     * @param clazz
     * @param sql
     * @param param
     * @return
     */
    public List<T> getBeanList(Class<T> clazz, String sql, Object ... param) {

        Connection connection = JDBCUtil.getConnection();

        List<T> beanList = null;

        try {
            beanList = queryRunner.query(connection, sql, new BeanListHandler<>(clazz), param);
        } catch (SQLException e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        } finally {
            
            // 关闭数据库连接
            JDBCUtil.releaseConnection(connection);
            
        }

        return beanList;
    }
}

public class ViewBaseServlet extends HttpServlet {

    private TemplateEngine templateEngine;

    @Override
    public void init() throws ServletException {

        // 1.获取ServletContext对象
        ServletContext servletContext = this.getServletContext();

        // 2.创建Thymeleaf解析器对象
        ServletContextTemplateResolver templateResolver = new ServletContextTemplateResolver(servletContext);

        // 3.给解析器对象设置参数
        // ①HTML是默认模式，明确设置是为了代码更容易理解
        templateResolver.setTemplateMode(TemplateMode.HTML);

        // ②设置前缀
        String viewPrefix = servletContext.getInitParameter("view-prefix");

        templateResolver.setPrefix(viewPrefix);

        // ③设置后缀
        String viewSuffix = servletContext.getInitParameter("view-suffix");

        templateResolver.setSuffix(viewSuffix);

        // ④设置缓存过期时间（毫秒）
        templateResolver.setCacheTTLMs(60000L);

        // ⑤设置是否缓存
        templateResolver.setCacheable(true);

        // ⑥设置服务器端编码方式
        templateResolver.setCharacterEncoding("utf-8");

        // 4.创建模板引擎对象
        templateEngine = new TemplateEngine();

        // 5.给模板引擎对象设置模板解析器
        templateEngine.setTemplateResolver(templateResolver);

    }

    protected void processTemplate(String templateName, HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // 1.设置响应体内容类型和字符集
        resp.setContentType("text/html;charset=UTF-8");

        // 2.创建WebContext对象
        WebContext webContext = new WebContext(req, resp, getServletContext());

        // 3.处理模板数据
        templateEngine.process(templateName, webContext, resp.getWriter());
    }
}

<!-- 在上下文参数中配置视图前缀和视图后缀 -->
<context-param>
    <param-name>view-prefix</param-name>
    <param-value>/WEB-INF/view/</param-value>
</context-param>
<context-param>
    <param-name>view-suffix</param-name>
    <param-value>.html</param-value>
</context-param>