tomcat部署在centos6.8上的乱码问题

web访问经常会莫名其妙的出现各种乱码问题。按照我自己的理解，设置一个charSet的过滤器，代码如下：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;import java.io.ByteArrayOutputStream;
import java.io.OutputStreamWriter;  

public class Charset implements Filter {

    @Override//过滤器销毁
    public void destroy() {
        // TODO Auto-generated method stub

    }

    @Override//chain我感觉是对request的一次转发
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        //设置字符编码，解决乱码问题
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        response.setContentType("chatset=utf-8");
        chain.doFilter(request, response);//让目标执行，放行

    }

    @Override//过滤器初始化
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub

    }

      private static String getDefaultCharSet() {
            OutputStreamWriter writer = new OutputStreamWriter(new ByteArrayOutputStream());
            String enc = writer.getEncoding();
            return enc;
        }  

}

然后在tomcat的conf目录下server.xml添加那么一句   URIEncoding="UTF-8"

 <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443"   URIEncoding="UTF-8"   />

最后记得每个jsp的开头都要记得  pageEncoding="utf-8"

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

基本上javaWeb的开发就不会出现什么乱码问题了。　

然后想得深入些，String类里面有个方法  String.getBytes()  ，这个方法JDK的源码是这样子的

@Deprecated
    public void getBytes(int srcBegin, int srcEnd, byte dst[], int dstBegin) {
        if (srcBegin < 0) {
            throw new StringIndexOutOfBoundsException(srcBegin);
        }
        if (srcEnd > value.length) {
            throw new StringIndexOutOfBoundsException(srcEnd);
        }
        if (srcBegin > srcEnd) {
            throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
        }
        int j = dstBegin;
        int n = srcEnd;
        int i = srcBegin;
        char[] val = value;   /* avoid getfield opcode */

        while (i < n) {
            dst[j++] = (byte)val[i++];
        }
    }

    /**
     * Encodes this {@code String} into a sequence of bytes using the named
     * charset, storing the result into a new byte array.
     *
     * <p> The behavior of this method when this string cannot be encoded in
     * the given charset is unspecified.  The {@link
     * java.nio.charset.CharsetEncoder} class should be used when more control
     * over the encoding process is required.
     *
     * @param  charsetName
     *         The name of a supported {@linkplain java.nio.charset.Charset
     *         charset}
     *
     * @return  The resultant byte array
     *
     * @throws  UnsupportedEncodingException
     *          If the named charset is not supported
     *
     * @since  JDK1.1
     */
    public byte[] getBytes(String charsetName)
            throws UnsupportedEncodingException {
        if (charsetName == null) throw new NullPointerException();
        return StringCoding.encode(charsetName, value, 0, value.length);
    }

    /**
     * Encodes this {@code String} into a sequence of bytes using the given
     * {@linkplain java.nio.charset.Charset charset}, storing the result into a
     * new byte array.
     *
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with this charset‘s default replacement byte array.  The
     * {@link java.nio.charset.CharsetEncoder} class should be used when more
     * control over the encoding process is required.
     *
     * @param  charset
     *         The {@linkplain java.nio.charset.Charset} to be used to encode
     *         the {@code String}
     *
     * @return  The resultant byte array
     *
     * @since  1.6
     */
    public byte[] getBytes(Charset charset) {
        if (charset == null) throw new NullPointerException();
        return StringCoding.encode(charset, value, 0, value.length);
    }

    /**
     * Encodes this {@code String} into a sequence of bytes using the
     * platform‘s default charset, storing the result into a new byte array.
     *
     * <p> The behavior of this method when this string cannot be encoded in
     * the default charset is unspecified.  The {@link
     * java.nio.charset.CharsetEncoder} class should be used when more control
     * over the encoding process is required.
     *
     * @return  The resultant byte array
     *
     * @since      JDK1.1
     */
    public byte[] getBytes() {
        return StringCoding.encode(value, 0, value.length);
    }

如果不指定String.getBytes()里面的参数，它会调用系统默认的参数，也就是java虚拟机的默认参数，查看这个参数的方法如下所示

   System.out.println("Default Charset=" + java.nio.charset.Charset.defaultCharset());
   System.out.println("file.encoding=" + System.getProperty("file.encoding"));
   System.out.println("Default Charset=" + java.nio.charset.Charset.defaultCharset());
   System.out.println("Default Charset in Use=" + getDefaultCharSet());  

值得一提的是，当你使用sftp工具上传文件至服务器时，如果没有指定sftp协议的文件名格式，sftp工具会以你默认系统的编码（大部分windows的编码都是GBK）传送中文文件名给服务器，这时候如果服务器默认的编码方式不是GBK，那么你上传的文件名在服务器端显示都是乱码。

centos查看系统的编码方式的命令是  echo $LAN ，也可以输入 locale  命令查看系统的编码。

在tomcat7中，用get方式访问中文名的文件，如uploads/%E6%B5%8B%E8%AF%95.mp3

浏览器本身会借助url.enCode()把中文名，空格等等转化为%E8等等的web地址传输编码格式，然后servlet接收到这个地址后会先url.unCode换成普通的编码，然后再根据request.setContentType="UTF-8"来换成中文名，但是这样子设置tomcat的 URIEncoding="UTF-8" 又是闹得哪样？

所以说编码真的是一个很神奇的玩意，此帖后面还会更新。