首页 > 代码库 > Spring MVC学习

Spring MVC学习

Spring MVC 使我们可以简单地,开发灵活且松耦合的Web项目。

在Servlet 2.5及以下,servlet类需要在web.xml文件中,配置<servlet>元素,才能访问这个Servlet。

但在Spring MVC + Servlet 3.0下,通过实现WebApplicationInitializer 接口,便可实现等同web.xml的配置,做到无web.xml。然后可以在WebApplicationInitializer实现类中,通过Spring MVC的 DispatcherServlet配置Servlet。

下面用Maven构建一个,基于注解和Java配置的,无web.xml配置的Spring MVC工程:

1、构建Maven项目,pom.xml文件如下:

<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.qfedu</groupId>
    <artifactId>SpringMVC</artifactId>
    <version>1.0</version>
    <packaging>war</packaging>

    <properties>
        <!-- Generic properties -->
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        
        <!-- build plugins -->
        <compiler.version>3.6.1</compiler.version>
        <war.version>3.1.0</war.version>

        <!-- Web -->
        <jsp.version>2.2</jsp.version>
        <jstl.version>1.2</jstl.version>
        <servlet.version>3.1.0</servlet.version>

        <!-- Spring -->
        <spring-framework.version>4.3.9.RELEASE</spring-framework.version>

        <!-- Logging -->
        <logback.version>1.2.3</logback.version>
        <slf4j.version>1.7.25</slf4j.version>
    </properties>
    
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${compiler.version}</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>${war.version}</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>

        <!-- Spring MVC -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>

        <!-- Other web dependency -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>${jstl.version}</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>${servlet.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>${jsp.version}</version>
            <scope>provided</scope>
        </dependency>

        <!-- Spring and Transactions -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>

        <!-- 使用 SLF4J 和 LogBack 作为日志 -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>${logback.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>${logback.version}</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-access</artifactId>
            <version>${logback.version}</version>
        </dependency>
    </dependencies>
</project>

在Maven的src / main / resources 目录下,新建logback.xml文件,用来配置日志:

<?xml version="1.0" encoding="UTF-8"?>
<configuration sacn="true" scanPeriod="1 seconds">
    <contextListener class="ch.qos.logback.classic.jul.LevelChangePropagator">
        <resetJUL>true</resetJUL>
    </contextListener>
    
    <jmxConfiguration />
    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>logbak: %d{HH:mm:ss.SSS} %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <!-- 将org.springframework.web包下的类的日志级别, 设置为DEBUG, 可以看到Web开发中的, 更详细的错误信息 -->
    <logger name="org.springframework.web" level="DEBUG" />
    <root level="info">
        <appender-ref ref="console" />
    </root>
</configuration>

依然在 src / main / resources 下,建立 views 目录,然后在views目录下,新建 index.jsp页面(内容随意) —— 页面没有放在Maven标准的src /main / webapp / WEB-INF下,这里的目的是,让大家熟悉Spring Boot的页面放置习惯,即放在src / main / resource目录下。(在Eclipse,用模板创建 jsp 页面时,不知道为什么,文件自动被移到了 webapp 目录下,因此如果是这样,需要再移回来)。

Spring MVC 的配置类:

package com.qfedu.springmvc.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import org.springframework.web.servlet.view.JstlView;

@Configuration
@EnableWebMvc
@ComponentScan("com.qfedu.springmvc")
public class MyMvcConfig {
    @Bean
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
        viewResolver.setPrefix("/WEB-INF/classes/views/");
        viewResolver.setSuffix(".jsp");
        viewResolver.setViewClass(JstlView.class);
        return viewResolver;
    }
}

ViewResolver用于映射开发时的路径,与视图的真实位置。因此,对于开发路径 src / main / resource / views,ViewResolver需要将路径前缀配置为 / WEB-INF / classes / views / ,因为运行时页面会自动编译到该目录下。如图:

技术分享

Web —— Servlet配置:

package com.qfedu.springmvc.config;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRegistration.Dynamic;

import org.springframework.web.WebApplicationInitializer;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;

//实现了WebApplicationInitializer接口, 将会被启动容器的类SpringServletContainerInitializer获取到并完成配置, 就和web.xml一样
public class WebInitializer implements WebApplicationInitializer {
    
    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        //新建WebApplicationContext,并注册配置类(注册配置类中返回的ViewResolver bean),关联当前的ServletContext
        AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
        context.register(MyMvcConfig.class);
        context.setServletContext(servletContext);
        
        //DispatcherServlet:前端控制器
        //用WebApplicationContext新建Spring MVC的 DispatcherServlet,然后注册并返回Servlet注册对象
        Dynamic servlet = servletContext.addServlet("dispatcher", new DispatcherServlet(context));
        //设置DispatcherServlet的Mapping和LoadOnStartUp次序
        servlet.addMapping("/");
        servlet.setLoadOnStartup(1);
    }

}

一个基本的控制器:

package com.qfedu.springmvc.controller;

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

@Controller
public class HomeContoller {
    @RequestMapping("/index")
    public String index() {
        return "index";
    }
}

最后部署到服务器上。

以上步骤即可完成一个比较基本的Spring MVC 项目。

Spring MVC学习