Spring(三）：使用java config配置spring mvc

时间：2022-05-25 20:33:28

一.配置DispatcherServlet
通常使用web.xml配置，此处使用java代码配置
SpittrWebAppInitializer.java

package spittr.config;

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

public class SpittrWebAppInitializer 
extends AbstractAnnotationConfigDispatcherServletInitializer{

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

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

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

spring会自动查找继承AbstractDispatcherServletInitializer的类用来配置servlet容器，AbstractAnnotationConfigDispatcherServletInitializer继承了AbstractDispatcherServletInitializer，所以spring会自动查找到SpittrWebAppInitializer，用来配置servlet；
getServletMappings表示将/为前缀的路径映射到此servlet；getServletConfigClasses方法返回的类，DispatchServlet加载应用上下文时，会使用这些配置类中的bean；getRootConfigClasses方法返回的类，当ContextLoaderListener创建上下文时，会加载这些类中配置的bean；

二.配置spring mvc
WebConfig.java

package spittr.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
@ComponentScan(basePackages = "spittr.web")
public class WebConfig  extends WebMvcConfigurerAdapter {

    @Bean
    public ViewResolver viewResolver(){
        InternalResourceViewResolver resolver = 
                new InternalResourceViewResolver();

        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        resolver.setExposeContextBeansAsAttributes(true);

        return resolver;
    }

    @Override 
    public void configureDefaultServletHandling(
            DefaultServletHandlerConfigurer configurer){
        configurer.enable();
    }

}

@Configuration注解标识这是一个配置类，@EnableWebMvc注解启用spring mvc，@ComponentScan注解配置要扫描的组件，根据此配置来查找控制器；viewResolver方法，返回jsp视图解析器，用于映射jsp；configureDefaultServletHandling方法配置默认的sevlet，当请求匹配不到DispatchServlet的映射路径时，会使用默认的Servlet；

ContextLoaderListener使用的配置：
RootConfig.java

package spittr.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={"spitter"},
                excludeFilters={
                                @Filter(type=FilterType.ANNOTATION, value=EnableWebMvc.class)
                })
public class RootConfig {

}

三.编写控制器
HomeController.java

package spittr.web;

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

@Controller
public class HomeController {
@RequestMapping(value="/", method=GET)
public String home(){
return "home";
    }
}

@Controller注解基于@Component，会产生一个bean，此控制器的方法home根据注解@RequestMapping(value=”/”, method=GET)，匹配到url的/，方法是GET时，返回home，视图解析器，根据home，找到/WEB-INF/views/home.jsp返回；需要添加文件/WEB-INF/views/home.jsp
/WEB-INF/views/home.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ page session="false" %>
<html>
<head>
<title>Spittr</title>
<link rel="stylesheet"
type="text/css"
href="<c:url value="/resources/style.css" />" >

</head>

<body>
<h1>Welcome to Spitter</h1>

<a href="<c:url value="/spittles" />">Spittles</a>
<a href="<c:url value="/spitter/register" />">Register</a>
</body>
</html>

注意，解析此jsp文件依赖jar包jstl.jar、standard.jar，需要放到tomcat的lib或者应用的lib目录下；

四.测试
在tomcat的webapps下创建目录spittr，把类copy到webapps\spittr\WEB-INF\classes下，home.jsp文件copy到webapps\spittr\WEB-INF\views\home.jsp，启动tomcat
浏览器访问http://127.0.0.1:8080/spittr/
显示

Welcome to Spitter

Spittles Register

java config和xml配置的对应关系,参考Servlet 3 + Spring MVC零配置：去除所有xml

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