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Spring Web MVC 框架

Spring Web MVC 框架

Spring MVC 框架,这个框架适用于 Web 开发的,它代替了 servlet 的页面跳转。

本篇是对 Spring MVC 框架的一个简单讲解,不会讲理论只是,如果想进一步学习的话,可以看 Spring MVC 简易教程

知识点

  • Spring Web Hello World 例子
  • Spring MVC 表单处理例子
  • Spring MVC 页面重定向例子
  • Spring MVC 异常处理例子

Spring Web Hello World 例子

首先创建一个新的项目

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mvn archetype:generate -DgroupId=com.learn-DartifactId=springMVCTest -DarchetypeArtifactId=maven-archetype-webapp

修改 pom.xml 文件,添加 Spring 的依赖:

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<project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.learn</groupId>
<artifactId>springMVCTest</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>springMVCTest Maven Webapp</name>
<url>http://maven.apache.org</url>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<spring.version>5.1.1.RELEASE</spring.version>
</properties>

<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.2</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<!--jetty maven 插件,为 maven 提供运行 web 程序的能力-->
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>9.4.12.v20180830</version>
<configuration>
<scanIntervalSeconds>10</scanIntervalSeconds>
<webApp>
<contextPath>/</contextPath>
</webApp>
</configuration>
</plugin>
</plugins>
</build>
</project>

修改 web.xml 文件内容如下:

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<?xml version = "1.0" encoding = "UTF-8"?>
<web-app xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xmlns = "http://java.sun.com/xml/ns/javaee" xmlns:web = "http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation = "http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id = "WebApp_ID" version = "3.0">
<display-name>springMVCTest</display-name>

<!-- 配置 Spring MVC DispatchcerServlet 前端控制器 -->
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<!-- contextConfigLocation 是参数名称,该参数的值包含 Spring MVC 的配置文件路径 -->
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/springmvc-config.xml</param-value>
</init-param>
<!-- 在 Web 应用启动时立即加载 Servlet -->
<load-on-startup>1</load-on-startup>
</servlet>
<!-- Servlet 映射声明 -->
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<!-- 监听当前域的所有请求 -->
<url-pattern>/</url-pattern>
</servlet-mapping>
<!-- 添加 register.jsp 为首页 -->
<welcome-file-list>
<welcome-file>register.jsp</welcome-file>
</welcome-file-list>
</web-app>

在 web.xml 中配置了 DispatchcerServlet,DispatchcerServlet 加载时需要一个 Spring MVC 的配置文件,默认会去 WEB-INF 下查找对应的 servlet-name-servlet.xml 文件,如本例中默认查找的是 springmvc-servlet.xml。

Spring MVC 的配置文件可以放在任何地方,用 servlet 的子元素 init-param 描述即可,见上述示例代码,这时 DispatchcerServlet 就会去查找 /WEB-INF/springmvc-config.xml。

在 webapp/WEB-INF/ 目录下新建 Spring MVC 配置文件 springmvc-config.xml,配置 Spring MVC 的 Controller,添加如下代码:

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<?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-4.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd">

<!-- 开启注解 -->
<mvc:annotation-driven />
<!-- 配置自动扫描的包,完成 Bean 的创建和自动依赖注入的功能 -->
<context:component-scan base-package = "com.learn.controller" />
<!-- 默认静态资源处理 -->
<mvc:default-servlet-handler/>
<!-- 配置视图解析器 -->
<bean id = "viewResolver" class = "org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name = "prefix" value = "/WEB-INF/views/"></property>
<property name = "suffix" value = ".jsp"></property>
</bean>
</beans>

在包 com.learn.controller 下新建 HelloController 类 HelloController.java,具体解释注释已经给出,代码如下:

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package com.learn.controller;

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

/**
* Controller 是一个基于注解的控制器
* 可以同时处理多个请求动作
*/
@Controller
public class HelloController {
/**
* RequestMapping 用来映射一个请求和请求的方法
* value = "/hello" 表示请求由 hello 方法进行处理
*/
@RequestMapping(value = "/hello")
public String hello() {
// 返回一个字符串 "success" 作为视图名称
return "hello";
}
}

在 webapp/WEB-INF 目录下新建文件夹 views,并在该路径下新建一个 JSP 页面命名为 hello.jsp,代码如下:

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<html>
<body>
<h2>Hello World!</h2>
</body>
</html>

输入 mvn jetty:run 运行程序,访问 spring mvc。

地址 127.0.0.1:8080/hello

效果:

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springMVCTest/ $ curl 127.0.0.1:8080/hello
<html>
<body>
<h2>Hello World!</h2>
</body>
</html>%

Spring MVC 表单处理

在项目目录 src/main/java 的包 com.learn.entity 下新建类 User.java,包含 id、username、password 和 age 属性,代码如下:

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package com.learn.entity;

import java.io.Serializable;

public class User implements Serializable {

private static final long serialVersionUID = 1L;
private Integer id;
private String username;
private String password;
private Integer age;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

public Integer getAge() {
return age;
}

public void setAge(Integer age) {
this.age = age;
}

}

在包 com.learn.controller 下新建 Controller 类 UserController.java,具体解释注释已经给出,代码如下:

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package com.learn.controller;

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

import com.learn.entity.User;

/**
* UserController 是一个基于注解的控制器
* 可以同时处理多个请求动作
*/
@Controller
public class UserController {
/**
* RequestMapping 用来映射一个请求和请求的方法
* value = "/register" 表示请求由 register 方法进行处理
*/
@RequestMapping(value = "/register")
public String Register(User user, Model model) { // user:视图层传给控制层的表单对象;model:控制层返回给视图层的对象
// 在 model 中添加一个名为 "user" 的 user 对象
model.addAttribute("user", user);
// 返回一个字符串 "success" 作为视图名称
return "success";
}
}

在 webapp 目录下新建一个 JSP 页面命名为 register.jsp,代码如下:

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<%@ page language = "java" contentType = "text/html; charset = UTF-8"
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>register page</title>
</head>
<body>
<form action="register" method="post">
<h5>User registration</h5>
<p>
<label>name </label>
<input type="text" id="username" name="username" tabindex="1" />
</p>

<p>
<label>password </label>
<input type="text" id="password" name="password" tabindex="2" />
</p>

<p>
<label>age </label>
<input type="text" id="age" name="age" tabindex="3" />
</p>
<p id="buttons">
<input id="submit" type="submit" tabindex="4" value="register" />
<input id="reset" type="reset" tabindex="5" value="reset" />
</p>
</form>
</body>
</html>

在 webapp/WEB-INF/views 新建一个 JSP 页面命名为 success.jsp,代码如下:

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<%@ page language = "java" contentType = "text/html; charset = UTF-8"
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>success page</title>
</head>
<body>
<h5>login was successful</h5>
<p>
name:${requestScope.user.username}<br />
password:${requestScope.user.password}<br />
age:${requestScope.user.age}<br />
</p>
</body>
</html>

输入 mvn jetty:run 运行程序

然后在 浏览器直接访问 之前的地址即可

Spring 页面重定向

修改 HelloController.java 代码如下

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package com.learn.controller;

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

@Controller
public class HelloController {

@RequestMapping(value = "/hello")
public String hello() {
return "hello";
}

@RequestMapping(value = "/redirect")
public String redirect(){
return "redirect:finalPage";
}

@RequestMapping(value = "/finalPage")
public String finalPage(){
return "final";
}
}

修改 hello.jsp 代码如下:

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<%@ page contentType = "text/html; charset = UTF-8" language = "java" %>
<%@taglib uri = "http://www.springframework.org/tags/form" prefix = "form"%>
<html>
<head>
<title>Spring MVC页面重定向</title>
</head>
<body>
<h2>Spring MVC页面重定向</h2>
<p>点击下面的按钮将结果重定向到新页面</p>
<form:form method = "GET" action = "redirect">
<table>
<tr>
<td><input type = "submit" value = "页面重定向" /></td>
</tr>
</table>
</form:form>
</body>
</html>

在同目录下新建 final.jsp,代码如下:

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<%@ page contentType = "text/html; charset = UTF-8" language = "java" %>
<%@taglib uri = "http://www.springframework.org/tags/form" prefix = "form"%>
<html>
<head>
<title>Spring重定向页面</title>
</head>
<body>
<h2>重定向页面...</h2>
</body>
</html>

输入 mvn jetty:run 运行程序

然后访问 127.0.0.1:8080/hello 地址即可

Spring MVC 异常处理

在 com.learn.controller 包下新建 ExceptionIntegratedHandleController.java,代码如下:

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package com.learn.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class ExceptionIntegratedHandleController {

@RequestMapping("/exceptionIntegratedHandleController/{id}")
@ResponseBody
public Object hello(@PathVariable String id) {

if (id.equals("1")) {
throw new RuntimeException("我这里是手动抛出的异常,期望被SpringMVC集中处理");
} else if (id.equals("2")) {
int value = 1 / 0;
return "手动运算错误";
} else {
return "no exception";
}
}
}

然后在 com.learn.exception 包下新建 MySpringExceptionIntegratedHandler.java,代码如下:

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package com.learn.exception;

import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

// 自己手动编写 Java 代码来实现定制异常信息处理
public class MySpringExceptionIntegratedHandler implements HandlerExceptionResolver {
@Override
public ModelAndView resolveException(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, Object handler, Exception ex) {
// 这里可以根据异常的类型来决定什么样的对策
System.out.println("异常已经被处理了");
System.out.println("异常的类型是:" + ex.getClass().getName());
request.setAttribute("ex", ex);
return new ModelAndView("runtimeExceptionPage");
}
}

然后在 springmvc-config.xml 中加入:

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<bean id = "mySpringExceptionIntegratedHandler" class = "com.learn.exception.MySpringExceptionIntegratedHandler"/>

最后在 views 目录下新建一个 runtimeExceptionPage.jsp,代码如下:

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<%@ page contentType = "text/html; charset = UTF-8"%>
<html>
<head><title>Exception!</title></head>
<body>
<% Exception e = (Exception)request.getAttribute("ex"); %>
<H2>业务错误: <%= e.getClass().getSimpleName()%></H2>
<hr />
<P>错误描述:</P>
<%= e.getMessage()%>
<P>错误信息:</P>
<% e.printStackTrace(new java.io.PrintWriter(out)); %>
</body>
</html>

输入 mvn jetty:run 运行程序

ND2HUg.md.png

文章作者: Depravity-pig
文章链接: https://magicconch17.github.io/2020/06/26/java-spring-web-mvc-framwork-2020-06-26/
版权声明: 本博客所有文章除特别声明外,均采用 CC BY-NC-SA 4.0 许可协议。转载请注明来自 Cat at ngint
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