为什么在春天使用控制器不显示文本？

Question

我正在尝试使用控制器显示文本，但没有得到任何输出。您能否告诉我，当我获取静态数据时，我在哪里做错了，它显示在浏览器上。但是当我想使用控制器显示时，我无法在此处显示是我的代码。

web.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
        <context-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/applicationContext.xml</param-value>
        </context-param>
        <listener>
            <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
        </listener>
        <servlet>
            <servlet-name>dispatcher</servlet-name>
            <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
            <load-on-startup>2</load-on-startup>
        </servlet>
        <servlet-mapping>
            <servlet-name>dispatcher</servlet-name>
            <url-pattern>*.htm</url-pattern>
        </servlet-mapping>
        <session-config>
            <session-timeout>
                30
            </session-timeout>
        </session-config>
        <welcome-file-list>
            <welcome-file>redirect.jsp</welcome-file>
        </welcome-file-list>
    </web-app>
**dispatcher-servlet.xml**
<?xml version='1.0' encoding='UTF-8' ?>
<!-- was: <?xml version="1.0" encoding="UTF-8"?> -->
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:context="http://www.springframework.org/schema/context"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       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-4.0.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">

    <bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>

    <!--
    Most controllers will use the ControllerClassNameHandlerMapping above, but
    for the index controller we are using ParameterizableViewController, so we must
    define an explicit mapping for it.
    -->

    <context:component-scan base-package="com.tutorialspoint" />
    <bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <props>
                <prop key="index.htm">indexController</prop>
            </props>
        </property>
    </bean>

    <bean id="viewResolver"
          class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          p:prefix="/WEB-INF/jsp/"
          p:suffix=".jsp" />

    <!--
    The index controller.
    -->
    <bean name="indexController"
          class="org.springframework.web.servlet.mvc.ParameterizableViewController"
          p:viewName="index" />

</beans>

redirect.jsp

 <%@page contentType="text/html" pageEncoding="UTF-8"%>
    <% response.sendRedirect("index.htm"); %>

applicationContext.xml

<?xml version='1.0' encoding='UTF-8' ?>
<!-- was: <?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:p="http://www.springframework.org/schema/p"
       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-4.0.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">


</beans>

ss.java 在 com.tutorialspoint 包中； 包 com.tutorialspoint;

import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 *
 * @author nksharma
 */
@Controller
@RequestMapping("/hello")
public class ss{

   @RequestMapping(method = RequestMethod.GET)
   public String printHello(ModelMap model) {
      model.addAttribute("message", "Hello Spring MVC Framework!");
      return "index";
   }

}

当我将 index.jsp 作为静态页面时。并像那样运行 http://localhost:8080/secondProject。它显示页面包含文本 这是测试 和 url 变成 http://localhost:8080/secondProject/index.htm

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Welcome to Spring Web MVC project</title>
    </head>

    <body>
        <p>This is test</p>
    </body>
</html>

现在我想从控制器获取数据并更改 index.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Welcome to Spring Web MVC project</title>
    </head>

    <body>
        <p>${message}</p>
    </body>
</html>

所以为什么我的输出不会显示预期的输出是“Hello Spring MVC Framework！”

Answer 1

由于您正在重定向，浏览器会发出新的请求。在这个过程中，模型属性会丢失。所以你需要在重定向场景中使用RedirectAttributes：

@RequestMapping(method = RequestMethod.GET)
public String printHello(ModelMap model, RedirectAttributes model) {
   model.addAttribute("message", "Hello Spring MVC Framework!");
   return "index";
}

Answer 2

使用 ModelAndView 对象

@RequestMapping(method = RequestMethod.GET)     
public ModelAndView printHello(){       
       ModelAndView model = new ModelAndView();         
       model.setViewName("index");      
       model.addObject("message", "Hello Spring MVC Framework!");
       return model;    
}