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範例詳解SpringMVC入門使用

2021-12-08 16:00:17

MVC模式(Model-View-Controller)是軟體工程中的一種軟體架構模式,把軟體系統分為三個基本部分:模型(Model),檢視(View)和控制器(Controller).通過分層使開發的軟體結構更清晰,從而達到開發效率的提高,可維護性和擴充套件性得到提高.Spring提供的MVC框架是在J2EE Web開發中對MVC模式的一個實現,本文通過範例講解一下Spring MVC 的使用.

先來看一個HTTP request在Spring的MVC框架是怎麼被處理的:(圖片來源於Spring in Action)

1,DispatcherServlet是Spring MVC的核心,它的本質是一個實現了J2EE標準中定義的HttpServlet,通過在web.xml設定<servlet-mapping>,來實現對request的監聽.

	<servlet>
		<servlet-name>springTestServlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<load-on-startup>2</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>springTestServlet</servlet-name>
		<url-pattern>*.do</url-pattern>
	</servlet-mapping>

** 以.do結尾的request都會由springTestServlet來處理.

2,3,當接受到request的時候,DispatcherServlet根據HandlerMapping的設定(HandlerMapping的組態檔預設根據<servlet-name>的值來決定,這裡會讀取springTestServlet-servlet.xml來獲得HandlerMapping的設定資訊),呼叫相應的Controller來對request進行業務處理.

	<bean id="simpleUrlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
		<property name="mappings">
			<props>
				<prop key="/login.do">loginController</prop>
			</props>
		</property>
	</bean>
	<bean id="loginController" class="com.test.spring.mvc.contoller.LoginController">
		<property name="sessionForm">
			<value>true</value>
		</property>
		<property name="commandName">
			<value>loginCommand</value>
		</property>
		<property name="commandClass">
			<value>com.test.spring.mvc.commands.LoginCommand</value>
		</property>
		<property name="authenticationService">
			<ref bean="authenticationService"/>
		</property>
		<property name="formView">
			<value>login</value>
		</property>
		<property name="successView">
			<value>loginDetail</value>
		</property>
	</bean>

** 以login.do結尾的request由loginController來處理.<property name="formView">設定的是Controller接收到HTTP GET請求的時候需要顯示的邏輯檢視名,本例是顯示login.jsp,<property name="successView">設定的是在接收到HTTP POST請求的時候需要顯示的邏輯檢視名,在本例中即login.jsp提交的時候需要顯示名為loginDetail的邏輯檢視.

4,Controller進行業務處理之後,返回一個ModelAndView物件.

return new ModelAndView(getSuccessView(),"loginDetail",loginDetail);

5,6,DispatcherServlet根據ViewResolver的設定(本例是在springTestServlet-servlet.xml檔案中設定)將邏輯view轉換到真正要顯示的View,如JSP等.

	<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="viewClass">
			<value>org.springframework.web.servlet.view.JstlView</value>
		</property>
		<property name="prefix">
			<value>/jsp/</value>
		</property>
		<property name="suffix">
			<value>.jsp</value>
		</property>
	</bean>

**其作用是將Controller中返回的ModleAndView解析到具體的資源(JSP檔案),如上例中的return new ModelAndView(getSuccessView();按照上面ViewResolver設定,會解析成/jsp/loginDetail.jsp.規則為prefix+ModelAndView的第二個引數+suffix.

範例的完整程式碼如下:

1web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
	<display-name>
	prjSpring3</display-name>
	<servlet>
		<servlet-name>springTestServlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<load-on-startup>2</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>springTestServlet</servlet-name>
		<url-pattern>*.do</url-pattern>
	</servlet-mapping>
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
	<listener>
		<listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>
	</listener>
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>/WEB-INF/springTest-services.xml</param-value>
	</context-param>
	<jsp-config>
		<taglib>
			<taglib-uri>/spring</taglib-uri>
			<taglib-location>/WEB-INF/spring.tld</taglib-location>
		</taglib>
	</jsp-config>
</web-app>
2,springTestServlet-servlet.xml的內容如下:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
	<bean id="simpleUrlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
		<property name="mappings">
			<props>
				<prop key="/login.do">loginController</prop>
			</props>
		</property>
	</bean>
	<bean id="loginController" class="com.test.spring.mvc.contoller.LoginController">
		<property name="sessionForm">
			<value>true</value>
		</property>
		<property name="commandName">
			<value>loginCommand</value>
		</property>
		<property name="commandClass">
			<value>com.test.spring.mvc.commands.LoginCommand</value>
		</property>
		<property name="authenticationService">
			<ref bean="authenticationService"/>
		</property>
		<property name="formView">
			<value>login</value>
		</property>
		<property name="successView">
			<value>loginDetail</value>
		</property>
	</bean>
	<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="viewClass">
			<value>org.springframework.web.servlet.view.JstlView</value>
		</property>
		<property name="prefix">
			<value>/jsp/</value>
		</property>
		<property name="suffix">
			<value>.jsp</value>
		</property>
	</bean>
</beans>

3,springTest-services.xml的內容:

 <bean id="authenticationService" class="com.test.spring.mvc.services.AuthenticationService"/>

4,Java程式碼:

public class LoginController extends SimpleFormController {
	org.springframework.web.servlet.DispatcherServlet t;
	protected ModelAndView onSubmit(Object command) throws Exception{		
		LoginCommand loginCommand = (LoginCommand) command;
		authenticationService.authenticate(loginCommand);
		LoginDetail loginDetail = authenticationService.getLoginDetail(loginCommand.getUserId());
		return new ModelAndView(getSuccessView(),"loginDetail",loginDetail);
	}	
	private AuthenticationService authenticationService;
	public AuthenticationService getAuthenticationService() {
		return authenticationService;
	}
	public void setAuthenticationService(
			AuthenticationService authenticationService) {
		this.authenticationService = authenticationService;
	}
	....
public class LoginCommand {
	private String userId;
	private String password;
	....
public class LoginDetail {
	private String userName;
public class AuthenticationService {		
	public void authenticate(LoginCommand command) throws Exception{
		if(command.getUserId()!= null && command.getUserId().equalsIgnoreCase("test") 
				&& command.getPassword()!= null && command.getPassword().equalsIgnoreCase("test")){	
		}else{
			throw new Exception("User id is not authenticated"); 
		}
	}
	public LoginDetail getLoginDetail(String userId){
		return new LoginDetail(userId);
	}
}	

5,JSP檔案:放在web-inf的jsp資料夾內

login.jsp:
<html><head>
<title>Login to Spring Test</title></head>
<body>
<h1>Please enter your userid and password.</h1>
<form method="post" action="login.do">
<table width="95%" bgcolor="f8f8ff" border="0" cellspacing="0" cellpadding="5">
<tr>
<td alignment="right" width="20%">User id:</td>
<td width="20%"><input type="text" name="userId" value="test"></td>
<td width="60%">
</tr>
<tr>
<td alignment="right" width="20%">Password:</td>
<td width="20%"><input type="password" name="password" value="test"></td>
<td width="60%">
</tr>
</table>
<br>
<input type="submit" alignment="center" value="login">
</form>
</body>
</html>
 
loginDetail.jsp:
<%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix="c"%> 
<html><head>
<title>Login to Spring Test</title></head>
<body>
<h1>Login Details:</h1>
<br/>
Login as: <c:out value ="${loginDetail.userName}"/>
<br/>
<a href="/S3/login.do" rel="external nofollow" >logout</a>
</body>
</html>

在瀏覽器的位址列輸入http://localhost:8080/XXX/login.do進入login.jsp頁面.

對設定的一些擴充點:

1為HandlerMapping和Controller的設定指定檔名稱.

<servlet>  
    <servlet-name>springTestServlet</servlet-name>  
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
    <init-param>  
        <param-name>contextConfigLocation</param-name>  
        <param-value>classpath*:/xxx.xml</param-value>  
    </init-param>  
    <load-on-startup>1</load-on-startup>  
</servlet>  

2,加入對MVC註解的支援:

<?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:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	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/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
	<context:annotation-config />
	<context:component-scan base-package="com.test.spring.mvc.contoller" />
	<mvc:annotation-driven />
 
@Controller
public class AnnotationController {
    @RequestMapping("annotation.do")
    protected void test(HttpServletRequest request,
            HttpServletResponse response) throws Exception{        
        response.getWriter().println("test Spring MVC annotation");
    }

3,註解和SimpleFormController同時使用需要在DispatcherServlet對應的servlet組態檔(本例是springTestServlet-servlet.xml)裡面設定:

<bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"/>
 
否則會發生下面的異常:
javax.servlet.ServletException: No adapter for handler [[email protected]]: Does your handler implement a supported interface like Controller?
	org.springframework.web.servlet.DispatcherServlet.getHandlerAdapter(DispatcherServlet.java:982)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:770)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:552)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

在WEB應用中的context組態檔通過下面的方式load,ContextLoaderListener是一個實現了ServletContextListener的listener,
它能夠存取<context-param>而得到組態檔的路徑,載入後初始化了一個WebApplicationContext,並且將其作為Attribute放在了servletContext中,
所有可以存取servletContext的地方則可以存取WebApplicationContext.

	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>
			/WEB-INF/springTest-services.xml,
			classpath:conf/jndiDSAppcontext.xml
		</param-value>
	</context-param>

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