spring boot web相关配置

spring boot集成了servlet容器，当我们在pom文件中增加spring-boot-starter-web的maven依赖时，不做任何web相关的配置便能提供web服务，这还得归于spring
boot 自动配置的功能（因为加了EnableAutoConfiguration的注解），帮我们创建了一堆默认的配置，以前在web.xml中配置，现在都可以通过spring bean的方式进行配置，由spring来进行生命周期的管理，大多数情况下，我们需要重载这些配置（例如修改服务的启动端口，contextpath,filter,listener,servlet,session超时时间等）

1. servlet配置

当应用只有默认的servlet（即DispatcherServlet）时，映射的url为/,存在其他的servlet时，映射的路径为servlet的注册的beanname(可通过@Component注解修改)，创建方式如下：

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@Component("myServlet")

public class MyServlet implements Servlet{

/**

*

* @see javax.servlet.Servlet#destroy()

*/

@Override

public void destroy() {

System.out.println("destroy...");

}

/**

* @return

* @see javax.servlet.Servlet#getServletConfig()

*/

@Override

public ServletConfig getServletConfig() {

return null;

}

/**

* @return

* @see javax.servlet.Servlet#getServletInfo()

*/

@Override

public String getServletInfo() {

return null;

}

/**

* @param arg0

* @throws ServletException

* @see javax.servlet.Servlet#init(javax.servlet.ServletConfig)

*/

@Override

public void init(ServletConfig arg0) throws ServletException {

System.out.println("servlet init...");

}

/**

* @param arg0

* @param arg1

* @throws ServletException

* @throws IOException

* @see javax.servlet.Servlet#service(javax.servlet.ServletRequest, javax.servlet.ServletResponse)

*/

@Override

public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException,

IOException {

System.out.println("service...");

}

2. filter配置

filter配置的映射是/*，创建方式如下：

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@Component("myFilter")

public class MyFilter implements Filter{

/**

*

* @see javax.servlet.Filter#destroy()

*/

@Override

public void destroy() {

System.out.println("destroy...");

}

/**

* @param arg0

* @param arg1

* @param arg2

* @throws IOException

* @throws ServletException

* @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)

*/

@Override

public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)

throws IOException,

ServletException {

System.out.println("doFilter...");

arg2.doFilter(arg0, arg1);

}

/**

* @param arg0

* @throws ServletException

* @see javax.servlet.Filter#init(javax.servlet.FilterConfig)

*/

@Override

public void init(FilterConfig arg0) throws ServletException {

System.out.println("filter init...");

}

}<span style="font-family: Arial, Helvetica, FreeSans, sans-serif; font-size: 13.3333330154419px; line-height: 17.3333339691162px; background-color: transparent;"> </span>

3. listener配置

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@Component("myListener")

public class MyListener implements ServletContextListener{

/**

* @param arg0

* @see javax.servlet.ServletContextListener#contextDestroyed(javax.servlet.ServletContextEvent)

*/

@Override

public void contextDestroyed(ServletContextEvent arg0) {

System.out.println("contextDestroyed...");

}

/**

* @param arg0

* @see javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)

*/

@Override

public void contextInitialized(ServletContextEvent arg0) {

System.out.println("listener contextInitialized...");

}

}

如果觉得控制力度不够灵活（例如你想修改filter的映射），spring boot还提供了

ServletRegistrationBean，FilterRegistrationBean，ServletListenerRegistrationBean这3个东西来进行配置

修改filter的映射

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@Configuration

public class WebConfig {

@Bean

public FilterRegistrationBean filterRegistrationBean(MyFilter myFilter){

FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();

filterRegistrationBean.setFilter(myFilter);

filterRegistrationBean.setEnabled(true);

filterRegistrationBean.addUrlPatterns("/bb");

return filterRegistrationBean;

}

}

4. 配置servlet 容器

可以通过两种方式配置servlet容器，一种是通过properties文件，例如：

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server.port=8081

server.address=127.0.0.1

server.sessionTimeout=30

server.contextPath=/springboot

完整的配置信息可以看这 http://github.com/spring-projects/spring-boot/tree/master/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

另一种方式是java代码的形式：

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@Component

public class MyCustomizationBean implements EmbeddedServletContainerCustomizer {

/**

* @param container

* @see org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer#customize(org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer)

*/

@Override

public void customize(ConfigurableEmbeddedServletContainer container) {

container.setContextPath("/sprintboot");

container.setPort(8081);

container.setSessionTimeout(30);

}

}

5. error 处理

spring boot 提供了/error映射来进行错误处理，它会返回一个json来对错误信息进行描述（包含了http状态和异常信息）,例如404的错误



当然可以定制错误页面，通过实现ErrorController接口，并将它装配起来即可，如下：

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@Controller

public class ErrorHandleController implements ErrorController {

/**

* @return

* @see org.springframework.boot.autoconfigure.web.ErrorController#getErrorPath()

*/

@Override

public String getErrorPath() {

return "/screen/error";

}

@RequestMapping

public String errorHandle(){

return getErrorPath();

}

}

还可以这样：

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@Component

private class MyCustomizer implements EmbeddedServletContainerCustomizer {

@Override

public void customize(ConfigurableEmbeddedServletContainer container) {

container.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/screen/error"));

}

}

6.模板引擎

spring boot 会自动配置 FreeMarker,Thymeleaf,Velocity，只需要在pom中加入相应的依赖即可，例如应用Velocity

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<dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-velocity</artifactId>

</dependency>

默认配置下spring boot会从src/main/resources/templates目录中去找模板

7.
jsp限制

如果要在spring boot中使用jsp,得将应用打包成war,这里有配置的example https://github.com/spring-projects/spring-boot/tree/master/spring-boot-samples/spring-boot-sample-web-jsp