Servlet中配置和使用过滤器的步骤记录

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.IOException;

public class CharacterEncodingFilter implements Filter {

    private String encoding;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // 从web.xml中获取配置的字符编码，如果没有配置则使用默认的UTF-8
        encoding = filterConfig.getInitParameter("encoding");
        if (encoding == null) {
            encoding = "UTF-8";
        }
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
        // 设置请求的字符编码
        request.setCharacterEncoding(encoding);
        // 设置响应的字符编码
        response.setContentType("text/html;charset=" + encoding);
        // 将请求传递给下一个过滤器或Servlet
        filterChain.doFilter(request, response);
    }

    @Override
    public void destroy() {
        // 释放资源，这里没有需要释放的资源，所以为空方法
    }
}

import javax.servlet.Filter;
import javax.servlet.annotation.WebFilter;

@WebFilter(filterName = "CharacterEncodingFilter", urlPatterns = "/*")
public class CharacterEncodingFilter implements Filter {
    // 过滤器类的实现代码
}

<web-app>
    <!-- 过滤器定义 -->
    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>com.example.CharacterEncodingFilter</filter-class>
        <!-- 过滤器初始化参数 -->
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </filter>

    <!-- 过滤器映射 -->
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>