文章目录
  1. 1. 1、去除web.xml
  2. 2. 2、去除Spring MVC配置文件dispatcher-servlet.xml
  3. 3. 3、去除Spring配置文件applicationContext.xml
  4. 4. 4、修改MyWebAppInitializer.java

在一些基于Spring/Spring MVC的Java Web项目中,总是会有一些xml配置文件,如web.xml、applicationContext.xml等,本文的目标即消灭这些xml配置文件,用代码和注解来代替。

由于本文是基于Servlet 3,所以首先需要准备支持Servlet 3的容器,例如Tomcat 7.0及以上版本、Jetty 8及以上版本。

1、去除web.xml

下面是一个典型的web.xml,包含Spring/Spring MVC的配置:

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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">


<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:dispatcher-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

</web-app>

Spring MVC提供了一个接口WebApplicationInitializer,用于替代web.xml配置文件。实现该接口的类会在Servlet容器启动时自动加载并运行。

将以上xml文件转换成Java代码:

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public class MyWebAppInitializer implements WebApplicationInitializer {

/**
* Servlet容器启动时会自动运行该方法
*/

@Override
public void onStartup(ServletContext servletContext) throws ServletException {

servletContext.setInitParameter("contextConfigLocation", "classpath:applicationContext.xml");

ServletRegistration.Dynamic registration = servletContext.addServlet("dispatcher", new DispatcherServlet());
registration.setLoadOnStartup(1);
registration.addMapping("/");
registration.setInitParameter("contextConfigLocation", "classpath:dispatcher-servlet.xml");

servletContext.addListener(new ContextLoaderListener());
}
}

此时即可删除web.xml文件,程序同样可以运行。

2、去除Spring MVC配置文件dispatcher-servlet.xml

一个典型的Spring MVC配置文件如下:

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd">


<mvc:annotation-driven />

<context:component-scan base-package="com.xxg.controller" />

<bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>

</beans>

Spring提供了@Configuration注解用于替代xml配置文件,@Bean注解可以替代xml中的<bean>来创建bean。

将以上xml配置文件转换成Java代码:

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@Configuration
@EnableWebMvc
@ComponentScan(basePackages = "com.xxg.controller")
public class WebConfig {

@Bean
public InternalResourceViewResolver internalResourceViewResolver() {
InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
viewResolver.setPrefix("/WEB-INF/jsp/");
viewResolver.setSuffix(".jsp");
return viewResolver;
}
}

3、去除Spring配置文件applicationContext.xml

Spring的配置文件中内容可能会比较多,并且不同的项目会有不同的配置,以下提供了一个简单的配置:

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">


<context:component-scan base-package="com.xxg">
<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller" />
</context:component-scan>

<context:property-placeholder location="classpath:config.properties"/>

<bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="${jdbc.driverClassName}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>

</beans>

其中数据库的相关配置从config.properties配置文件读取:

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jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mydb
jdbc.username=root
jdbc.password=123456

将以上xml配置转换成Java代码:

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@Configuration
@ComponentScan(basePackages = "com.xxg", excludeFilters = {@Filter(value = Controller.class)})
public class AppConfig {

@Value("${jdbc.driverClassName}")
private String driverClassName;

@Value("${jdbc.url}")
private String url;

@Value("${jdbc.username}")
private String username;

@Value("${jdbc.password}")
private String password;

@Bean(destroyMethod = "close")
public DataSource dataSource() {
BasicDataSource dataSource = new BasicDataSource();
dataSource.setDriverClassName(driverClassName);
dataSource.setUrl(url);
dataSource.setUsername(username);
dataSource.setPassword(password);
return dataSource;
}

/**
* 必须加上static
*/

@Bean
public static PropertyPlaceholderConfigurer loadProperties() {
PropertyPlaceholderConfigurer configurer = new PropertyPlaceholderConfigurer();
ClassPathResource resource = new ClassPathResource("config.properties");
configurer.setLocations(resource);
return configurer;
}
}

除了上面的方法外,加载properties配置文件还可以使用@PropertySource注解:

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@Configuration
@ComponentScan(basePackages = "com.xxg", excludeFilters = {@Filter(value = Controller.class)})
@PropertySource("classpath:config.properties")
public class AppConfig {

@Value("${jdbc.driverClassName}")
private String driverClassName;

@Value("${jdbc.url}")
private String url;

@Value("${jdbc.username}")
private String username;

@Value("${jdbc.password}")
private String password;

@Bean(destroyMethod = "close")
public DataSource dataSource() {
BasicDataSource dataSource = new BasicDataSource();
dataSource.setDriverClassName(driverClassName);
dataSource.setUrl(url);
dataSource.setUsername(username);
dataSource.setPassword(password);
return dataSource;
}

/**
* 必须加上static
*/

@Bean
public static PropertySourcesPlaceholderConfigurer loadProperties() {
PropertySourcesPlaceholderConfigurer configurer = new PropertySourcesPlaceholderConfigurer();
return configurer;
}
}

以上两种Java实现方式选择其中一种即可。

4、修改MyWebAppInitializer.java

完成以上步骤后,就可以去掉dispatcher-servlet.xml和applicationContext.xml等Spring配置文件,用Java代码替代了。

此时,第1步中的MyWebAppInitializer.java需要修改,不再读取xml配置文件,而是加载@Configuration注解的Java代码来配置Spring:

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public class MyWebAppInitializer implements WebApplicationInitializer {

/**
* Servlet容器启动时会自动运行该方法
*/

@Override
public void onStartup(ServletContext servletContext) throws ServletException {

AnnotationConfigWebApplicationContext rootContext = new AnnotationConfigWebApplicationContext();
rootContext.register(AppConfig.class);
servletContext.addListener(new ContextLoaderListener(rootContext));

AnnotationConfigWebApplicationContext webContext = new AnnotationConfigWebApplicationContext();
webContext.register(WebConfig.class);
ServletRegistration.Dynamic registration = servletContext.addServlet("dispatcher", new DispatcherServlet(webContext));
registration.setLoadOnStartup(1);
registration.addMapping("/");
}
}

至此,便完成了Java程序替换xml配置文件所有工序。

文章目录
  1. 1. 1、去除web.xml
  2. 2. 2、去除Spring MVC配置文件dispatcher-servlet.xml
  3. 3. 3、去除Spring配置文件applicationContext.xml
  4. 4. 4、修改MyWebAppInitializer.java