如何用Java类配置Spring MVC(不通过web.xml和XML方式)

DispatcherServlet是Spring MVC的核心,按照传统方式, 需要把它配置到web.xml中. 我个人比较不喜欢XML配置方式, XML看起来太累, 冗长繁琐. 还好借助于Servlet 3规范和Spring 3.1的功能增强, 可以采用一种全新的,更简洁的方式配置Spring MVC了. 下面按这种方式一个Hello World的MVC配置.

Step 1:先用eclipse创建一个Maven的WEB工程. 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>ocr</groupId>
  <artifactId>ocr</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <javaee-api.version>7.0</javaee-api.version>
        <spring.version>4.2.0.RELEASE</spring.version>
        <junit.version>4.12</junit.version>
    </properties>

    <dependencies>
         <dependency>
              <groupId>javax</groupId>
              <artifactId>javaee-api</artifactId>
              <version>${javaee-api.version}</version>
        </dependency>
        <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>${junit.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.1.3</version>
        </dependency>
    </dependencies>


    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.6</version>
                <configuration>
                    <warSourceDirectory>WebContent</warSourceDirectory>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Step 2: 配置DispatcherServlet. 需要创建一个Web初始化类OcrWebAppInitializer, 继承自AbstractAnnotationConfigDispatcherServletInitializer

package com.chry.ocr.config;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class OcrWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class<?>[] { RootConfig.class };
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class<?>[] { WebConfig.class };        //ָ指定Web配置类
    }

    @Override
    protected String[] getServletMappings() {    //将DispatcherServlet映射到"/"
        return new String[] { "/" };
    }

}

Step 3: 配置Spring MVC视图解析WebConfig.java, 需要要创建一个类继承自WebMvcConfigurerAdapter

package com.chry.ocr.config;

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

@Configuration
@EnableWebMvc                                //启动SpringMVC
@ComponentScan("com.chry.ocr.controller")            //启动组件扫描
public class WebConfig extends WebMvcConfigurerAdapter {

    //配置JSP视图解析器
    @Bean
    public ViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        resolver.setExposeContextBeansAsAttributes(true);
        return resolver;
    }
    
    //配置静态资源的处理
    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();        //对静态资源的请求转发到容器缺省的servlet，而不使用DispatcherServlet
    }
    
}

Step 4: 配置RootConfig.java

package com.chry.ocr.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.ComponentScan.Filter;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

@Configuration
@ComponentScan( basePackages={"com.chry.ocr"}, 
                excludeFilters = { @Filter(type=FilterType.ANNOTATION,value=EnableWebMvc.class)}
              )

public class RootConfig {

}

至此, 传统方式中需要通过web.xml进行配置的东西就已将全部完成有上面三个java类(OcrWebAppInitializer, RootConfig, WebConfig)完成. 可以开始写Controller和页面代码了

Step 5: 编写一个HomeController.java, 它将输出"hello World from Spring MVC"到home.jsp页面

package com.chry.ocr.controller;

import static org.springframework.web.bind.annotation.RequestMethod.*;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class HomeController {
    @RequestMapping(value = "/", method=GET)
    public ModelAndView home() {
        String message = "Hello world from Spring MVC";
        return new ModelAndView("home", "message", message);
    }
}

Step 6: 编写一个jsp页面, 按照我们在视图解析器和Controller里面的配置,放在WEB-INF/views/home.jsp中

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Spring MVC Tutorial chry</title>
<style type="text/css">
</style>
</head>
<body>
    <br>
    <div style='text-align:center;'>
        ${message}
    </div>
</body>

Step 7: 至此所有工作完成, 使用maven的"clean install"选项进行编译打包后,在执行,访问http://localhost:8080即可. 页面效果和工程结构如下,工程里面没有web.xml