JAVA配置字符过滤器

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/thebigdipperbdx/article/details/86688534

介绍

• Filter也称之为过滤器，它是Servlet技术中最实用的技术，Web开发人员通过Filter技术，对WEB服务器管理的所有WEB资源：例如JSP, Servlet, 静态图片文件或静态 HTML文件等进行拦截，从而实现一些特殊的功能。例如实现URL级别的权限访问控制、过滤敏感词汇、压缩响应信息等一些高级功能。

• Filter主要用于对用户请求进行预处理，也可以对HttpServletResponse进行后处理。使用Filter的完整流程：Filter对用户请求进行预处理，接着将请求交给Servlet进行处理并生成响应，最后Filter再对服务器响应进行后处理。

源码

package org.springframework.web.filter;

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.util.Assert;

/**
 * Servlet Filter that allows one to specify a character encoding for requests.
 * This is useful because current browsers typically do not set a character
 * encoding even if specified in the HTML page or form.
 */
public class CharacterEncodingFilter extends OncePerRequestFilter {

	private String encoding;
	private boolean forceRequestEncoding = false;
	private boolean forceResponseEncoding = false;

	public CharacterEncodingFilter() {
	}
	
	public CharacterEncodingFilter(String encoding) {
		this(encoding, false);
	}
	
	public CharacterEncodingFilter(String encoding, boolean forceEncoding) {
		this(encoding, forceEncoding, forceEncoding);
	}

	public CharacterEncodingFilter(String encoding, boolean forceRequestEncoding, boolean forceResponseEncoding) {
		Assert.hasLength(encoding, "Encoding must not be empty");
		this.encoding = encoding;
		this.forceRequestEncoding = forceRequestEncoding;
		this.forceResponseEncoding = forceResponseEncoding;
	}

	public void setEncoding(String encoding) {
		this.encoding = encoding;
	}

	public String getEncoding() {
		return this.encoding;
	}

	public void setForceEncoding(boolean forceEncoding) {
		this.forceRequestEncoding = forceEncoding;
		this.forceResponseEncoding = forceEncoding;
	}

	public void setForceRequestEncoding(boolean forceRequestEncoding) {
		this.forceRequestEncoding = forceRequestEncoding;
	}

	public boolean isForceRequestEncoding() {
		return this.forceRequestEncoding;
	}

	public void setForceResponseEncoding(boolean forceResponseEncoding) {
		this.forceResponseEncoding = forceResponseEncoding;
	}

	public boolean isForceResponseEncoding() {
		return this.forceResponseEncoding;
	}


	@Override
	protected void doFilterInternal(
			HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		String encoding = getEncoding();
		if (encoding != null) {
			if (isForceRequestEncoding() || request.getCharacterEncoding() == null) {
				request.setCharacterEncoding(encoding);
			}
			if (isForceResponseEncoding()) {
				response.setCharacterEncoding(encoding);
			}
		}
		filterChain.doFilter(request, response);
	}

}

• 使用Spring提供的过滤器，只需要在web.xml中配置即可

<filter>
	<description>字符集过滤器</description>
	<filter-name>encodingFilter</filter-name>
	<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
	<init-param>
		<description>字符集编码</description>
		<param-name>encoding</param-name>
		<param-value>UTF-8</param-value>
	</init-param>
</filter>
<filter-mapping>
	<filter-name>encodingFilter</filter-name>
	<url-pattern>/*</url-pattern>
</filter-mapping>

自定义字符过滤器

• 需实现接口javax.servlet.Filter

package cn.sh.sstic.smet.comm.filter;
 
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
 
public class EncodingFilter implements Filter {
	private String charset = "UTF-8";
	
	
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
                throws IOException, ServletException {
		request.setCharacterEncoding(this.charset);
		chain.doFilter(request, response);
	}
	
	public void init(FilterConfig arg0) {
		this.charset = arg0.getInitParameter("charset");
	}
 
	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		
	}
}

源码

package javax.servlet;

import java.io.IOException;

// Referenced classes of package javax.servlet:
//            ServletException, FilterConfig, ServletRequest, ServletResponse, 
//            FilterChain

public interface Filter
{

    public abstract void init(FilterConfig filterconfig)
        throws ServletException;

    public abstract void doFilter(ServletRequest servletrequest, ServletResponse servletresponse, FilterChain filterchain)
        throws IOException, ServletException;

    public abstract void destroy();
}