java之Maven配置和springMvc的简单应用

初始springMvc这个框架，非常的陌生，而且幸好公司是通过maven这个代码管理工具，可以随时添加依赖。解决了很多问题在以后深入开发中。

项目结构：

通过结构中，pom.xml这个文件其实就说明这个项目是通过maven构建的，pom.xml里是主要负责构建jar或者war的依赖。其代码如下：

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>taofuxn_web</groupId>
    <artifactId>springMvc</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>springMvc Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>

    
       <!-- spring需要的jar包 -->  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-context</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
        </dependency>  
  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-core</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
        </dependency>  
  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-beans</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
        </dependency>  
  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-webmvc</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
        </dependency>  
  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-orm</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
        </dependency>  
    
    
  </dependencies>
  <build>
    <finalName>springMvc</finalName>
  </build>
</project>

从中可以看出，如果要设置依赖jar，那么就要知道jar的相关信息。如何得知呢....

寻师问友后，得到了一个站点http://mvnrepository.com/，搜索你要的那个依赖，里面有相应的版本。

关于springMvc和maven的配置就上面的pom.xml，当然还可以配置Mybxxxs，hibernate..

接下来就要应用springmvc 的相关配置了：

首先配置的是 项目中的web.xml，其代码如下：

<?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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>springmvc</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  
    <servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
            <!-- 可以自定义servlet.xml配置文件的位置和名称，默认为WEB-INF目录下，名称为[<servlet-name>]-servlet.xml，如spring-servlet.xml-->
             <init-param>
                <param-name>contextConfigLocation</param-name>
                <param-value>/WEB-INF/spring-servlet.xml</param-value>
            </init-param> 
    
        <load-on-startup>1</load-on-startup>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>spring</servlet-name>
        <!-- mvc-拦截所有的请求 -->
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    
</web-app>

根据上面的注释我们知道要再相应的目录下手动的新建一个spring-servlet.xml文件进行spring的配置信息

其次spring-servlet.xml的代码如下：

<?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:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">
        
        <!-- 激活注解的的标签 -->
        <context:annotation-config/>
        
        <!-- 只搜索有controller注解的类，同时这个包名别搞错了，不然就找不到controller -->
   　　 <context:component-scan base-package="cn.taofu" >
       　　 <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
   　　 </context:component-scan>
    
    　　<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        　　<property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
        　　<property name="prefix" value="/WEB-INF/jsps/" /><!-- 这个是配置在当下目录寻找jsp文件-->
       　　 <property name="suffix" value=".jsp" />
   　　 </bean>
</beans>

配置好了web.xml和spring-servlet.xml，基本的spring的运行环境就有了，接下来就要生成一个测试controller

package cn.taofu;

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

@Controller
@RequestMapping("/test")
public class TestController {
    
    @RequestMapping("/mvc")
    public String getMode(){
        
        System.out.println("hello springmvc");
        
        return "index";
    }
}

好吧，这是最简单的应用了，只要在相应的目录下生成index.jsp文件。当请求访问该方法上的mvc连接时就会跳转到index.jsp,访问的链接如：localhost:8080/springMvc/test/mvc   ->回车。基本就能调通这个前后

代码虽然入门初级，运行起来了我也是掉了块肉了。当然其中的问题也不少。

问题一、在启动服务器出现的报错信息

java.lang.ClassNotFoundException: org.springframework.web.servlet.DispatcherServlet
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
    at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:525)
    at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:507)
    at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:126)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1099)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1043)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4957)
    at org.apache.catalina.core.StandardContext$3.call(StandardContext.java:5284)
    at org.apache.catalina.core.StandardContext$3.call(StandardContext.java:5279)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)

　　这种错误很郁闷，单凭初级的开发是很难确定是什么问题，所有只有去到顶级程序员的家栈溢出，发现如下解决办法：

　　这个方法标注了，只有maven构建的应用，如不是还是多去google吧

You need to add the "Maven Dependency" in the Deployment Assembly

   - right click on your project and choose properties.
   - click  on Deployment Assembly.
   - click add
   - click on "Java Build Path Entries"
   - select Maven Dependencies"
   - click Finish.

Rebuild and deploy again

Note: This is also applicable for *non maven* project.

问题二、少了两个jar,

message Handler processing failed; nested exception is java.lang.NoClassDefFoundError: javax/servlet/jsp/jstl/core/Config
 
description The server encountered an internal error that prevented it from fulfilling this request.
 
exception
 
org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.NoClassDefFoundError: javax/servlet/jsp/jstl/core/Config
    org.springframework.web.servlet.DispatcherServlet.triggerAfterCompletionWithError(DispatcherServlet.java:1259)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause
 
java.lang.NoClassDefFoundError: javax/servlet/jsp/jstl/core/Config
    org.springframework.web.servlet.support.JstlUtils.exposeLocalizationContext(JstlUtils.java:97)
    org.springframework.web.servlet.view.JstlView.exposeHelpers(JstlView.java:135)
    org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:211)
    org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:263)
    org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
    org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

　这种错误比较好找，百度一下发现需要两个jar.于是导入如下文件解决

过程是很艰难的，但结果还是可以的。努力