Spring与Web环境集成

#Spring与Web环境集成| 来源: 网络整理| 查看: 265

1.Spring与Web环境集成 1.1自定义监听器将Spring集成到web环境

1_需求:将spring集成到web开发环境中,将所有的bean对象创建交给spring,除了servlet,servlet可以理解为一个测试类.在servlet中获取ApplicationContext,获取对应的bean

环境搭建,这个是自己一步步取实现的,其实spring有提供简单的方法完成1.1的操作

org.springframework spring-context 5.0.5.RELEASE org.springframework spring-webmvc 5.0.5.RELEASE javax.servlet servlet-api 2.5 javax.servlet.jsp jsp-api 2.0 //1.创建dao层接口和实现类 //dao接口 IUserDao public interface IUserDao{ void save(); } //UserDaoImpl实现类 public class UserDaoImpl implements IUserDao{ @Override public void save(){ System.out.printLn("正在保存..."); } } //2.创建service业务层接口和实现类 public interface IUserService{ void save(); } //UserServletImpl实现类 public class UserServiceImpl implements IUserService{ private IUserDao userDao; //为依赖注入提供set方法 public void setUserDao(IUserDao userDao){this userDao=userDao;} @Override public void save(){ userDao.save(); } } /*web包下创建UserServlet类内部功能:调Spring容器,创建service对象,调sava()方法*/ public class UserServlet extends HttpServlet{ @Override//复写doGet方法 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{ //通过配置文件获取上下文 ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); //获取bean,因为只有一个UserServiceImpl,可以使用字节码的方法获取 UserServiceImpl userService = context.getBean(UserServiceImpl.class); //调用save方法 userService.save(); } } userServlet cn.ppvir.web.UserServlet userServlet /userServlet

最后配置tomcat,启动测试 http://localhost:80/userServlet

2_问题描述: spring在web开发环境下,每个servlet都需要new ClassPathXmlApplicationContext("applicationContext.xml") 因为配置文件会加载多次,所以会造成性能浪费

3_改进一: 将ApplicationContext对象的创建交给监听器创建,监听器将创建好的对象存入ServletContext域对象中,在servlet中直接获取该对象.

编写监听器代码 import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; public class ContextLoaderListener implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent servletContextEvent) { //获取上下文 ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); //将spring获取到的应用上下文,保存到servletContext域中 ServletContext servletContext = servletContextEvent.getServletContext(); servletContext.setAttribute("context",context); //之后去web.xml配置listener监听器和改写servlet代码 } 监听器配置 web.xml cn.ppvir.listener.ContextLoaderListener servlet代码改写 public class UserServlet extends HttpServlet { /** * 改进一: * 将ApplicationContext对象的创建交给监听器创建,监听器将创建好的对象存入ServletContext域对象中,在servlet中直接取该对象即可 * * @param req * @param resp * @throws ServletException * @throws IOException */ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //获取servletContext域对象 ServletContext servletContext = this.getServletContext(); //从ServletContext域对象中,获取监听器创建的应用上下文,强转为ApplicationContext ApplicationContext context = (ApplicationContext) servletContext.getAttribute("context"); UserServiceImpl userService = context.getBean(UserServiceImpl.class); userService.save(); } }

重启tomcat完成测试.

4.优化二:

1_在web.xml文件中配置要加载的applicationContext.xml文件 web.xml contextConfigLocation classpath:applicationContext.xml 2.改写ContextLoaderListener监听器类,获取全局初始化参数 public class ContextLoaderListener implements ServletContextListener { /** * 优化二: 获取全局初始化参数 * * @param servletContextEvent */ @Override public void contextInitialized(ServletContextEvent servletContextEvent) { //获取域对象 ServletContext servletContext = servletContextEvent.getServletContext(); //从配置文件中获取applicationContext /* contextConfigLocation classpath:applicationContext.xml */ String contextConfigLocation = servletContext.getInitParameter("contextConfigLocation"); //获取应用上下文 ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(contextConfigLocation); //将Spring的应用上下文存储到ServletContext域对象中 servletContext.setAttribute("context",context); System.out.println("spring容器创建完毕..."); } } 3.优化强转ApplicationContext,使用工具类直接从servletContext域对象中获取applicationContext对象. //创建工具类 package cn.ppvir.listener; import org.springframework.context.ApplicationContext; import javax.servlet.ServletContext; /** * 工具类,强转context上下文为ApplicationContext */ public class WebApplicationContextUtils { /** * @param servletContext 参数是域对象 * @return 返回值是强转后的对象ApplicationContext */ public static ApplicationContext getWebapplicationContext(ServletContext servletContext){ return (ApplicationContext)servletContext.getAttribute("context"); } } 4.修改UserServlet类使用WebApplicationContextUtils优化强转context public class ContextLoaderListener implements ServletContextListener { /** * 优化二: 使用WebApplicationContextUtils工具类,简化强转上下文对象的操作 * @param req * @param resp * @throws ServletException * @throws IOException */ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //获取域对象 ServletContext servletContext = this.getServletContext(); ApplicationContext context = WebApplicationContextUtils.getWebapplicationContext(servletContext); UserServiceImpl userService = context.getBean(UserServiceImpl.class); userService.save(); } }

重启tomcat完成测试

1.2使用spring提供的监听器将spring集成到web环境

UserDao和UserService层与上面一样

导入依赖 pom.xml org.springframework spring-web 5.0.5.RELEASE 配置Spring提供的监听器ContextLoaderListener web.xml contextConfigLocation classpath:applicationContext.xml org.springframework.web.context.ContextLoaderListener service web.UserServlet service / applicationContext.xml配置让spring管理注入 applicationContext.xml servlet中通过工具获得应用上下文对象 public class UserServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //获取servletContext域对象 ServletContext servletContext = this.getServletContext(); //使用spring框架自带的WebApplicationContextUtils工具,获取上下文对象 WebApplicationContext context = WebApplicationContextUtils.getWebApplicationContext(servletContext); UserServiceImpl userService = context.getBean(UserServiceImpl.class); userService.save(); } } 1.3小结:

1.web环境中集成spring只需要配置监听器即可 2.Spring负责管理处=除了controller以外的所有bean对象

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Spring与Web环境集成

Spring与Web环境集成

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