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。