SpringMVC初体验---HELLOWORLD

SpringMVC最近大有赶超struts2的趋势。

乘着在学校有空对该框架做一定的熟悉和了解，争取毕业设计用这个框架完成

第一部建立一个web项目

maven构建语句，构建出一个空的web项目

mvn archetype:create -DgroupId=packageName -DartifactId=webappName -DarchetypeArtifactId=maven-archetype-webapp -Dwtpversion=1.0

接着在pom中加入spring MVC的依赖

<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.springframework.mvc</groupId>
  <artifactId>mvc</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>mvc Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <properties>
		<java-version>1.6</java-version>
		<org.springframework-version>3.1.0.RELEASE</org.springframework-version>
		<org.aspectj-version>1.6.10</org.aspectj-version>
		<org.slf4j-version>1.6.1</org.slf4j-version>
	</properties>
	<dependencies>
		<!-- Spring -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>${org.springframework-version}</version>
			<exclusions>
				<!-- Exclude Commons Logging in favor of SLF4j -->
				<exclusion>
					<groupId>commons-logging</groupId>
					<artifactId>commons-logging</artifactId>
				 </exclusion>
			</exclusions>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>${org.springframework-version}</version>
		</dependency>
		<!-- AspectJ -->
		<dependency>
			<groupId>org.aspectj</groupId>
			<artifactId>aspectjrt</artifactId>
			<version>${org.aspectj-version}</version>
		</dependency>	
		
		<!-- Logging -->
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>${org.slf4j-version}</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>jcl-over-slf4j</artifactId>
			<version>${org.slf4j-version}</version>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-log4j12</artifactId>
			<version>${org.slf4j-version}</version>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.16</version>
			<scope>runtime</scope>
		</dependency>

		<!-- @Inject -->
		<dependency>
			<groupId>javax.inject</groupId>
			<artifactId>javax.inject</artifactId>
			<version>1</version>
		</dependency>
				
		<!-- Servlet -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>servlet-api</artifactId>
			<version>2.5</version>
			<scope>provided</scope>
		</dependency>
		<dependency>
			<groupId>javax.servlet.jsp</groupId>
			<artifactId>jsp-api</artifactId>
			<version>2.1</version>
			<scope>provided</scope>
		</dependency>
		<dependency>
			<groupId>javax.servlet.jsp.jstl</groupId>
			<artifactId>jstl-api</artifactId>
			<version>1.2</version>
		</dependency>		
		<dependency>
			<groupId>org.glassfish.web</groupId>
			<artifactId>jstl-impl</artifactId>
			<version>1.2</version>
		</dependency>

		<!-- Jackson JSON Processor -->
		<dependency>
			<groupId>org.codehaus.jackson</groupId>
			<artifactId>jackson-mapper-asl</artifactId>
			<version>1.8.1</version>
		</dependency>

		<!-- Rome Atom+RSS -->
		<dependency>
			<groupId>net.java.dev.rome</groupId>
			<artifactId>rome</artifactId>
			<version>1.0.0</version>
		</dependency>
		
		<!-- JSR 303 with Hibernate Validator -->
		<dependency>
			<groupId>javax.validation</groupId>
			<artifactId>validation-api</artifactId>
			<version>1.0.0.GA</version>
		</dependency>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-validator</artifactId>
			<version>4.1.0.Final</version>
		</dependency>
		
		<!-- Joda Time Library -->	
		<dependency>
			<groupId>joda-time</groupId>
			<artifactId>joda-time</artifactId>
			<version>1.6.2</version>
		</dependency>

		<!-- File Upload -->
		<dependency>
			<groupId>commons-fileupload</groupId>
			<artifactId>commons-fileupload</artifactId>
			<version>1.2.2</version>
		</dependency>	
		<dependency>
			<groupId>commons-io</groupId>
			<artifactId>commons-io</artifactId>
			<version>2.0.1</version>
		</dependency>
			
		<!-- Test -->
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.8.2</version>
			<scope>test</scope>
		</dependency>
        
	</dependencies>
	<repositories>	
		<!-- For testing against latest Spring snapshots -->
		<repository>
			<id>org.springframework.maven.snapshot</id>
			<name>Spring Maven Snapshot Repository</name>
			<url>http://maven.springframework.org/snapshot</url>
			<releases><enabled>false</enabled></releases>
			<snapshots><enabled>true</enabled></snapshots>
		</repository>
		<!-- For developing against latest Spring milestones -->
		<repository>
			<id>org.springframework.maven.milestone</id>
			<name>Spring Maven Milestone Repository</name>
			<url>http://maven.springframework.org/milestone</url>
			<snapshots><enabled>false</enabled></snapshots>
		</repository>
	</repositories>
 <build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>2.3.2</version>				
				<configuration>
					<source>${java-version}</source>
					<target>${java-version}</target>
				</configuration>
			</plugin>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-dependency-plugin</artifactId>
				<executions>
					<execution>
						<id>install</id>
						<phase>install</phase>
						<goals>
							<goal>sources</goal>
						</goals>
					</execution>
				</executions>
			</plugin>
			<plugin>
				<groupId>org.codehaus.mojo</groupId>
				<artifactId>aspectj-maven-plugin</artifactId>
				<!-- Have to use version 1.2 since version 1.3 does not appear to work with ITDs -->
				<version>1.2</version>
				<dependencies>
					<!-- You must use Maven 2.0.9 or above or these are ignored (see MNG-2972) -->
					<dependency>
						<groupId>org.aspectj</groupId>
						<artifactId>aspectjrt</artifactId>
						<version>${org.aspectj-version}</version>
					</dependency>
					<dependency>
						<groupId>org.aspectj</groupId>
						<artifactId>aspectjtools</artifactId>
						<version>${org.aspectj-version}</version>
					</dependency>
				</dependencies>
				<executions>
					<execution>
						<goals>
							<goal>compile</goal>
							<goal>test-compile</goal>
						</goals>
					</execution>
				</executions>
				<configuration>
					<outxml>true</outxml>
					<source>${java-version}</source>
					<target>${java-version}</target>
				</configuration>
			</plugin>
			<plugin>
				<groupId>org.codehaus.mojo</groupId>
				<artifactId>tomcat-maven-plugin</artifactId>
				<version>1.1</version>
			</plugin>	
		</plugins>
	</build>
</project>

这样我们的依赖已经配置齐全了，接下来就是配置前端控制器FrontController在SpringMVC中是DispatcherServlet

他位于org.springframework.web.servlet.DispatcherServlet

在web.xml中配置

<!-- 处理所有请求 process all request -->
	<servlet>
		<servlet-name>FrontController</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
                        //会反射注入
			<param-name>contextConfigLocation</param-name>
			<param-value>/WEB-INF/spring/appServlet/servlet-context.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>

	<servlet-mapping>
		<servlet-name>FrontController</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>

我们看一下init-param为什么必须得叫做contextConfigLocation

首先看DispatcherServlet的构造方法

public DispatcherServlet() {
		super();
	}

查看父类发现有setContextConfigLocation方法

/**
	 * Set the context config location explicitly, instead of relying on the default
	 * location built from the namespace. This location string can consist of
	 * multiple locations separated by any number of commas and spaces.
	 */
	public void setContextConfigLocation(String contextConfigLocation) {
		this.contextConfigLocation = contextConfigLocation;
	}

查看是谁调用了这个方法

没人调用这个方法，那么假定这个方法是被反射调用的

再往父类上查找，可以在setContextConfigLocation处加一个断点，debug的时候就能看到是如何被调用的

/**
	 * Map config parameters onto bean properties of this servlet, and
	 * invoke subclass initialization.
	 * @throws ServletException if bean properties are invalid (or required
	 * properties are missing), or if subclass initialization fails.
	 */
	@Override
	public final void init() throws ServletException {
		if (logger.isDebugEnabled()) {
			logger.debug("Initializing servlet '" + getServletName() + "'");
		}

		// Set bean properties from init parameters.
		try {
                        //获得所有的属性值
                        PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
			ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, this.environment));
			initBeanWrapper(bw);
			bw.setPropertyValues(pvs, true);
		}
		catch (BeansException ex) {
			logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
			throw ex;
		}

		// Let subclasses do whatever initialization they like.
		initServletBean();

		if (logger.isDebugEnabled()) {
			logger.debug("Servlet '" + getServletName() + "' configured successfully");
		}
	}

通过AbstractPropertyAccessor往里面填充属性

public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid)
			throws BeansException {

		List<PropertyAccessException> propertyAccessExceptions = null;
		List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
				((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
		for (PropertyValue pv : propertyValues) {
			try {
				// This method may throw any BeansException, which won't be caught
				// here, if there is a critical failure such as no matching field.
				// We can attempt to deal only with less serious exceptions.
                                //往里面填充属性的核心方法
                                 setPropertyValue(pv);


			}
			catch (NotWritablePropertyException ex) {
				if (!ignoreUnknown) {
					throw ex;
				}
				// Otherwise, just ignore it and continue...
			}
			catch (NullValueInNestedPathException ex) {
				if (!ignoreInvalid) {
					throw ex;
				}
				// Otherwise, just ignore it and continue...
			}
			catch (PropertyAccessException ex) {
				if (propertyAccessExceptions == null) {
					propertyAccessExceptions = new LinkedList<PropertyAccessException>();
				}
				propertyAccessExceptions.add(ex);
			}
		}

		// If we encountered individual exceptions, throw the composite exception.
		if (propertyAccessExceptions != null) {
			PropertyAccessException[] paeArray =
					propertyAccessExceptions.toArray(new PropertyAccessException[propertyAccessExceptions.size()]);
			throw new PropertyBatchUpdateException(paeArray);
		}
	}

可以看到在BeanWrapperImp当中实现了setPropertyValue(String propertyName, Object value)方法

public void setPropertyValue(String propertyName, Object value) throws BeansException {
		BeanWrapperImpl nestedBw;
		try {
			nestedBw = getBeanWrapperForPropertyPath(propertyName);
		}
		catch (NotReadablePropertyException ex) {
			throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName,
					"Nested property in path '" + propertyName + "' does not exist", ex);
		}
		PropertyTokenHolder tokens = getPropertyNameTokens(getFinalPath(nestedBw, propertyName));
		nestedBw.setPropertyValue(tokens, new PropertyValue(propertyName, value));


	}

可以看到这里的确是反射调用的.

这样就完成了springMVC资源的载入

看下之前载入的资源文件做了什么

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:beans="http://www.springframework.org/schema/beans"
	xsi:schemaLocation="
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">
        <!-- 开启注解 -->
	<annotation-driven />
	
	<!--  引入用户定义的@Controller 用来处理请求 -->
	<beans:import resource="controllers.xml" />
	
</beans:beans>

再看一下controllers.xml

<?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:mvc="http://www.springframework.org/schema/mvc"
	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
		http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

   	<!--  自动扫描组件 -->
   	<context:component-scan base-package="com.springframework.helloworld" />
   	
</beans>

包扫描把所有有@controller注解的类spring会对其进行加载

@Controller  //注解表示自己是controller
public class SimpleController {
	//对应映射的路径  这里就表示 http://localhost/项目名/simple会映射到该控制器
	@RequestMapping("/simple")  
        //@ResponseBody表示这个返回的string将会当成输出值返回给浏览器
	public @ResponseBody String simple() {
		return  "hello world!";
	}

}

所有的处理完毕~ 放入tomcat第一个springMVC的Helloworld就诞生啦~

SpringMVC初体验---HELLOWORLD

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