基于注解的 Spring MVC 简单入门

怼烎@ 2022-08-07 12:43 205阅读 0赞

web.xml 配置：

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1.  <servlet>
2.  <servlet-name>dispatcher</servlet-name>
3.  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
4.  <init-param>
5.  <description>加载/WEB-INF/spring-mvc/目录下的所有XML作为Spring MVC的配置文件</description>
6.  <param-name>contextConfigLocation</param-name>
7.  <param-value>/WEB-INF/spring-mvc/\*.xml</param-value>
8.  </init-param>
9.  <load-on-startup>1</load-on-startup>
10. </servlet>
11. <servlet-mapping>
12. <servlet-name>dispatcher</servlet-name>
13. <url-pattern>\*.htm</url-pattern>
14. </servlet-mapping>

<servlet>
    	<servlet-name>dispatcher</servlet-name>
    	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    	<init-param>
    		<description>加载/WEB-INF/spring-mvc/目录下的所有XML作为Spring MVC的配置文件</description>
    		<param-name>contextConfigLocation</param-name>
    		<param-value>/WEB-INF/spring-mvc/*.xml</param-value>
    	</init-param>
    	<load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
    	<servlet-name>dispatcher</servlet-name>
    	<url-pattern>*.htm</url-pattern>
    </servlet-mapping>

这样，所有的.htm的请求，都会被DispatcherServlet处理；

初始化 DispatcherServlet 时，该框架在 web 应用程序WEB-INF 目录中寻找一个名为\[servlet-名称\]\-servlet.xml的文件，并在那里定义相关的Beans，重写在全局中定义的任何Beans，像上面的web.xml中的代码，对应的是dispatcher\-servlet.xml；当然也可以使用<init-param>元素，手动指定配置文件的路径；

**dispatcher\-servlet.xml 配置：**

1.  <?xml  version="1.0"  encoding="UTF-8"?>
2.  <beans  xmlns="http://www.springframework.org/schema/beans"
3.  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.  xmlns:mvc="http://www.springframework.org/schema/mvc"
5.  xmlns:p="http://www.springframework.org/schema/p"
6.  xmlns:context="http://www.springframework.org/schema/context"
7.  xmlns:aop="http://www.springframework.org/schema/aop"
8.  xmlns:tx="http://www.springframework.org/schema/tx"
9.  xsi:schemaLocation="http://www.springframework.org/schema/beans
10. http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
11. http://www.springframework.org/schema/context
12. http://www.springframework.org/schema/context/spring-context-3.0.xsd
13. http://www.springframework.org/schema/aop
14. http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
15. http://www.springframework.org/schema/tx
16. http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
17. http://www.springframework.org/schema/mvc
18. http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
19. http://www.springframework.org/schema/context
20. http://www.springframework.org/schema/context/spring-context-3.0.xsd">
21. 
24. <context:component-scan base-package="com.minx.crm.web.controller"/>
25. 
26. <bean  id="viewResolver"
27. class="org.springframework.web.servlet.view.InternalResourceViewResolver"
28. p:prefix="/WEB-INF/jsp/"
29. p:suffix=".jsp" />
30. </beans>

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:mvc="http://www.springframework.org/schema/mvc"
           xmlns:p="http://www.springframework.org/schema/p"
           xmlns:context="http://www.springframework.org/schema/context"
           xmlns:aop="http://www.springframework.org/schema/aop"
           xmlns:tx="http://www.springframework.org/schema/tx"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
    			http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    			http://www.springframework.org/schema/context 
    			http://www.springframework.org/schema/context/spring-context-3.0.xsd
    			http://www.springframework.org/schema/aop 
    			http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
    			http://www.springframework.org/schema/tx 
    			http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
    			http://www.springframework.org/schema/mvc 
    			http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
    			http://www.springframework.org/schema/context 
    			http://www.springframework.org/schema/context/spring-context-3.0.xsd">
        
        <context:component-scan base-package="com.minx.crm.web.controller"/>
       
        <bean id="viewResolver"
              class="org.springframework.web.servlet.view.InternalResourceViewResolver"
              p:prefix="/WEB-INF/jsp/"
              p:suffix=".jsp" />
    </beans>

第一个Controller：

1.  package com.minx.crm.web.controller;
2.  
3.  import org.springframework.stereotype.Controller;
4.  import org.springframework.web.bind.annotation.RequestMapping;
5.  @Controller
6.  public class IndexController \{
7.  @RequestMapping("/index")
8.  public String index() \{
9.  return "index";
10. \}
11. \}

package com.minx.crm.web.controller;
    
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    @Controller
    public class IndexController {
        @RequestMapping("/index")
        public String index() {
            return "index";
        }
    }

@Controller注解标识一个控制器，@RequestMapping注解标记一个访问的路径（/index.htm），return "index"标记返回视图（index.jsp）；

注：如果@RequestMapping注解在类级别上，则表示一相对路径，在方法级别上，则标记访问的路径；

**从@RequestMapping注解标记的访问路径中获取参数：**

Spring MVC 支持RESTful风格的URL参数，如：

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1.  @Controller
2.  public class IndexController \{
3.  
4.  @RequestMapping("/index/\{username\}")
5.  public String index(@PathVariable("username") String username) \{
6.  System.out.print(username);
7.  return "index";
8.  \}
9.  \}

@Controller
    public class IndexController {
    
        @RequestMapping("/index/{username}")
        public String index(@PathVariable("username") String username) {
            System.out.print(username);
            return "index";
        }
    }

在@RequestMapping中定义访问页面的URL模版，使用\{\}传入页面参数，使用@PathVariable 获取传入参数，即可通过地址：[http://localhost:8080/crm/index/tanqimin.htm][http_localhost_8080_crm_index_tanqimin.htm] 访问；

**根据不同的Web请求方法，映射到不同的处理方法：**

使用登陆页面作示例，定义两个方法分辨对使用GET请求和使用POST请求访问login.htm时的响应。**可以使用处理****GET****请求的方法显示视图，使用****POST****请求的方法处理业务逻辑**；

1.  @Controller
2.  public class LoginController \{
3.  @RequestMapping(value =  "/login", method = RequestMethod.GET)
4.  public String login() \{
5.  return "login";
6.  \}
7.  @RequestMapping(value =  "/login", method = RequestMethod.POST)
8.  public String login2(HttpServletRequest request) \{
9.  String username = request.getParameter("username").trim();
10. System.out.println(username);
11. return "login2";
12. \}
13. \}

@Controller
    public class LoginController {
        @RequestMapping(value = "/login", method = RequestMethod.GET)
        public String login() {
            return "login";
        }
        @RequestMapping(value = "/login", method = RequestMethod.POST)
        public String login2(HttpServletRequest request) {
                String username = request.getParameter("username").trim();
                System.out.println(username);
            return "login2";
        }
    }

在视图页面，通过地址栏访问login.htm，是通过GET请求访问页面，因此，返回登陆表单视图login.jsp；当在登陆表单中使用POST请求提交数据时，则访问login2方法，处理登陆业务逻辑；

防止重复提交数据，可以使用**重定向视图：**

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1.  return "redirect:/login2"

return "redirect:/login2"

**可以传入方法的参数类型：**

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1.  @RequestMapping(value =  "login", method = RequestMethod.POST)
2.  public String testParam(HttpServletRequest request, HttpServletResponse response, HttpSession session) \{
3.  String username = request.getParameter("username");
4.  System.out.println(username);
5.  return null;
6.  \}

@RequestMapping(value = "login", method = RequestMethod.POST)
    public String testParam(HttpServletRequest request, HttpServletResponse response, HttpSession session) {
    	String username = request.getParameter("username");
    	System.out.println(username);
    	return null;
    }

可以传入HttpServletRequest、HttpServletResponse、HttpSession，值得注意的是，如果第一次访问页面，HttpSession没被创建，可能会出错；

其中，String username = request.getParameter("username");可以转换为传入的参数：

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1.  @RequestMapping(value =  "login", method = RequestMethod.POST)
2.  public String testParam(HttpServletRequest request, HttpServletResponse response, HttpSession session,@RequestParam("username") String username) \{
3.  String username = request.getParameter("username");
4.  System.out.println(username);
5.  return null;
6.  \}

@RequestMapping(value = "login", method = RequestMethod.POST)
    public String testParam(HttpServletRequest request, HttpServletResponse response, HttpSession session,@RequestParam("username") String username) {
    	String username = request.getParameter("username");
    	System.out.println(username);
    	return null;
    }

使用@RequestParam 注解获取GET请求或POST请求提交的参数；

**获取Cookie的值：使用@CookieValue ：**

获取PrintWriter：

可以直接在Controller的方法中传入PrintWriter对象，就可以在方法中使用：

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1.  @RequestMapping(value =  "login", method = RequestMethod.POST)
2.  public String testParam(PrintWriter out,  @RequestParam("username") String username) \{
3.  out.println(username);
4.  return null;
5.  \}

@RequestMapping(value = "login", method = RequestMethod.POST)
    public String testParam(PrintWriter out, @RequestParam("username") String username) {
    	out.println(username);
    	return null;
    }

**获取表单中提交的值，并封装到POJO中，传入Controller的方法里：**

POJO如下（User.java）：

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1.  public class User\{
2.  private long id;
3.  private String username;
4.  private String password;
5.  
6.  …此处省略getter,setter...
7.  \}

public class User{
    	private long id;
    	private String username;
    	private String password;
    
    	…此处省略getter,setter...
    }

通过表单提交，直接可以把表单值封装到User对象中：

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1.  @RequestMapping(value =  "login", method = RequestMethod.POST)
2.  public String testParam(PrintWriter out, User user) \{
3.  out.println(user.getUsername());
4.  return null;
5.  \}

@RequestMapping(value = "login", method = RequestMethod.POST)
    public String testParam(PrintWriter out, User user) {
    	out.println(user.getUsername());
    	return null;
    }

**可以把对象，put 入获取的Map对象中，传到对应的视图：**

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1.  @RequestMapping(value =  "login", method = RequestMethod.POST)
2.  public String testParam(User user, Map model) \{
3.  model.put("user",user);
4.  return "view";
5.  \}

@RequestMapping(value = "login", method = RequestMethod.POST)
    public String testParam(User user, Map model) {
    	model.put("user",user);
    	return "view";
    }

在返回的view.jsp中，就可以根据key来获取user的值（通过EL表达式，$\{user \}即可）；

**Controller中方法的返回值：**

void：多数用于使用PrintWriter输出响应数据；

String 类型：返回该String对应的View Name；

任意类型对象：

返回ModelAndView：

**自定义视图（JstlView，ExcelView）：**

**拦截器（Inteceptors）：**

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1.  public class MyInteceptor implements HandlerInterceptor \{
2.  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object o)
3.  throws Exception \{
4.  return false;
5.  \}
6.  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object o, ModelAndView mav)
7.  throws Exception \{
8.  \}
9.  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object o, Exception excptn)
10. throws Exception \{
11. \}
12. \}

public class MyInteceptor implements HandlerInterceptor {
    	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object o) 
    		throws Exception {
    		return false;
    	}
    	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object o, ModelAndView mav) 
    		throws Exception {
    	}
    	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object o, Exception excptn) 
    		throws Exception {
    	}
    }

拦截器需要实现HandleInterceptor接口，并实现其三个方法：

preHandle：拦截器的前端，执行控制器之前所要处理的方法，通常用于权限控制、日志，其中，Object o表示下一个拦截器；

postHandle：控制器的方法已经执行完毕，转换成视图之前的处理；

afterCompletion：视图已处理完后执行的方法，通常用于释放资源；

在MVC的配置文件中，配置拦截器与需要拦截的URL：

1.  <mvc:interceptors>
2.  <mvc:interceptor>
3.  <mvc:mapping path="/index.htm" />
4.  <bean class="com.minx.crm.web.interceptor.MyInterceptor" />
5.  </mvc:interceptor>
6.  </mvc:interceptors>

<mvc:interceptors>
    	<mvc:interceptor>
    		<mvc:mapping path="/index.htm" />
    		<bean class="com.minx.crm.web.interceptor.MyInterceptor" />
    	</mvc:interceptor>
    </mvc:interceptors>

**国际化：**

在MVC配置文件中，配置国际化属性文件：

1.  <bean  id="messageSource"
2.  class="org.springframework.context.support.ResourceBundleMessageSource"
3.  p:basename="message">
4.  </bean>

那么，Spring就会在项目中搜索相关的国际化属性文件，如：message.properties、message\_zh\_CN.properties

在VIEW中，引入Spring标签：<%@taglib uri="[http://www.springframework.org/tags][http_www.springframework.org_tags]" prefix="spring" %>，使用<spring:message code="key" />调用，即可；

如果一种语言，有多个语言文件，可以更改MVC配置文件为：

1.  <bean  id="messageSource"  class="org.springframework.context.support.ResourceBundleMessageSource">
2.  <property  name="basenames">
3.  <list>
4.  <value>message01</value>
5.  <value>message02</value>
6.  <value>message03</value>
7.  </list>
8.  </property>
9.  </bean>

[view plain]: http://blog.csdn.net/superdog007/article/details/25835653#
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[http_localhost_8080_crm_index_tanqimin.htm]: http://localhost:8080/crm/index/tanqimin.htm
[http_www.springframework.org_tags]: http://www.springframework.org/tags