4.SpringBoot加载Filter汇总

1.传统的filter的加载方式

filter的组成部分

• filter配置类
• 拦截的路径
• 初始化参数
• 忽略的路径

<filter>
   <filter-name>TestFilter</filter-name>
    <filter-class>com.cppba.filter.TestFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>TestFilter</filter-name>
  <url-pattern>/*</url-pattern>
  <init-param>
    <param-name>paramName</param-name>
    <param-value>paramValue</param-value>
  </init-param>
</filter-mapping>

2.SpringBoot加载filter的方式（方法一）

2.1 SpringBoot加载filter的方式（方法一）

• .创建自定义Filter

import javax.servlet.*;
import java.io.IOException;

public class TestFilter implements Filter {
  @Override
  public void init(FilterConfig filterConfig) throws ServletException {

  }

  @Override
  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
      throws IOException, ServletException {
    System.out.println("TestFilter");
  }

  @Override
  public void destroy() {

  }
}

• .加载并初始化filter

@Bean
 public FilterRegistrationBean testFilterRegistration() {

   FilterRegistrationBean registration = new FilterRegistrationBean();
   registration.setFilter(new TestFilter());
   registration.addUrlPatterns("/*");
   registration.addInitParameter("paramName", "paramValue");
   registration.setName("testFilter");
   registration.setOrder(1);
   return registration;
 }

2.2.SpringBoot加载filter的方式（方法二）

• .创建自定义Filter

@Order(1)
//重点
@WebFilter(filterName = "testFilter1", urlPatterns = "/*")
public class TestFilterFirst implements Filter {
  @Override
  public void init(FilterConfig filterConfig) throws ServletException {

  }

  @Override
  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
      throws IOException, ServletException {
    System.out.println("TestFilter1");
    filterChain.doFilter(servletRequest,servletResponse);
  }

  @Override
  public void destroy() {

  }
}

比较核心的代码是自定义类上面加上@WebFilter；
其中@Order注解表示执行过滤顺序，值越小，越先执行
spring-boot的入口处加上如下注解@ServletComponentScan：

3. 配置多个时执行顺序设置

3.1 通过代码配置方式

在spring boot中的FilterRegistrationBean注册过滤器的类中有个order属性，
private int order = Ordered.LOWEST_PRECEDENCE;
细看源码可以知道，这个order的默认值是Integer.MAX_VALUE 也就是int的最大值，
spring boot 会按照order值的大小，从小到大的顺序来依次过滤。
再有一个过滤器的话，可以设置成 registration.setOrder(Integer.MAX_VALUE - 1)

/**
 * 配置过滤器
 * @return
 */
@Bean
 public FilterRegistrationBean someFilterRegistration() {
     FilterRegistrationBean registration = new FilterRegistrationBean();
     registration.setFilter(sessionFilter());
     registration.addUrlPatterns("/*");
     registration.addInitParameter("paramName", "paramValue");
     registration.setName("sessionFilter");
     registration.setOrder(Integer.MAX_VALUE);
     return registration;
 }

3.2 通过注解的方式设置

/**
 * 配置过滤器
 * @return
 */
@Bean
@Order(Integer.MAX_VALUE)
public FilterRegistrationBean someFilterRegistration() {
    FilterRegistrationBean registration = new FilterRegistrationBean();
    registration.setFilter(sessionFilter());
    registration.addUrlPatterns("/*");
    registration.addInitParameter("paramName", "paramValue");
    registration.setName("sessionFilter");
    return registration;
}