大家知道tomcat5.0开始,对网页的中文字符的post或者get,经常会出现乱码现象。

具体是因为Tomcat默认是按ISO-8859-1进行URL解码,ISO-8859-1并未包括中文字符,这样的话中文字符肯定就不能被正确解析了。

常见的解决方法是在tomcat的server.xml下的connetor属性中增加URIEncoding或者useBodyEncodingForURI属性。

但是,这两种方式有什么区别呢?

我简单谈一下自己的理解:

按照tomcat-docs/config/http.html文档的说明

URIEncoding:This specifies the character encoding used to decode the URI bytes, after %xx decoding the URL. If not specified, ISO-8859-1 will be used.

useBodyEncodingForURI:This specifies if the encoding specified in contentType should be used for URI query parameters, instead of using the URIEncoding.

也就是说,

useBodyEncodingForURI参数表示是否用request.setCharacterEncoding
参数对URL提交的数据和表单中GET方式提交的数据进行重新编码,在默认情况下,该参数为false。

URIEncoding参数指定对所有GET方式请求进行统一的重新编码(解码)的编码。

URIEncoding和useBodyEncodingForURI区别是,

URIEncoding是对所有GET方式的请求的数据进行统一的重新编码,

而useBodyEncodingForURI则是根据响应该请求的页面的request.setCharacterEncoding参数对数据进行的重新编码,不同的页面可以有不同的重新编码的编码

再详细点的======================================================================================================

本文章会从tomcat的源码角度来解析Tomcat的两个参数设置URIEncoding和useBodyEncodingForURI。

对于一个请求,常用的有两种编码方式,如下:

<!DOCTYPE html>  
<html>  
    <head>  
        <meta charset="utf-8" />  
        <title></title>  
    </head>  
    <body>  
        <form action="http://127.0.0.1:8080/string?name=中国" method="post">  
            <input type="text" name="user" value="张三"/>  
            <input type="submit" value="提交"/>  
        </form>  
    </body>  
</html>  

首先说说结论:
上述请求有两处含有中文,一处是请求参数中,即?name=‘中国’,另一处是请求体中,即user=‘张三’。对于这两处tomcat7是分两种编码方式的。URIEncoding就是针对请求参数的编码设置的,而filter的request.setCharacterEncoding(‘UTF-8’)或者请求header中的content-type中的编码都是针对请求体的。不要把他们搞混了。

useBodyEncodingForURI=true是说,请求参数的编码方式要采用请求体的编码方式。当useBodyEncodingForURI=true时,若请求体采用utf-8解析,则请求参数也要采用utf-8来解析。这两个属性值的设置在tomcat的conf/server.xml文件中配置,如下:


<Service name="Catalina"> <!--The connectors can use a shared executor, you can define one or more named thread pools--> <!-- <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" maxThreads="150" minSpareThreads="4"/> --> <!-- A "Connector" represents an endpoint by which requests are received and responses are returned. Documentation at : Java HTTP Connector: /docs/config/http.html (blocking & non-blocking) Java AJP Connector: /docs/config/ajp.html APR (HTTP/AJP) Connector: /docs/apr.html Define a non-SSL HTTP/1.1 Connector on port 8080 --> <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" useBodyEncodingForURI='true' URIEncoding='UTF-8' /> <!-- A "Connector" using the shared thread pool-->

这样写只是说明这两者的配置位置,并不是两个属性要同时配置,不要理解错了。
继续说说CharacterEncodingFilter的作用。
使用方式,将如下代码加入web.xml文件中:

<filter>  
        <filter-name>encoding</filter-name>  
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>  
        <init-param>  
            <param-name>encoding</param-name>  
            <param-value>UTF-8</param-value>  
        </init-param>  
        <init-param>  
            <param-name>forceEncoding</param-name>  
            <param-value>true</param-value>  
        </init-param>  
    </filter>  
  
    <filter-mapping>  
        <filter-name>encoding</filter-name>  
        <url-pattern>/*</url-pattern>  
    </filter-mapping>  

作用是,当forceEncoding为false的前提下(默认为false),当request没有指定content-type或content-type不含编码时,该filter将会为这个request设定请求体的编码为filter的encoding值。
当forceEncoding为true的前提下,就会为request的请求体和response都设定为这个filter的encoding值。
CharacterEncodingFilter源码如下:

public class CharacterEncodingFilter extends OncePerRequestFilter {  
  
    private String encoding;  
  
    private boolean forceEncoding = false;  
  
  
    /** 
     * Set the encoding to use for requests. This encoding will be passed into a 
     * {@link javax.servlet.http.HttpServletRequest#setCharacterEncoding} call. 
     * <p>Whether this encoding will override existing request encodings 
     * (and whether it will be applied as default response encoding as well) 
     * depends on the {@link #setForceEncoding "forceEncoding"} flag. 
     */  
    public void setEncoding(String encoding) {  
        this.encoding = encoding;  
    }  
  
    /** 
     * Set whether the configured {@link #setEncoding encoding} of this filter 
     * is supposed to override existing request and response encodings. 
     * <p>Default is "false", i.e. do not modify the encoding if 
     * {@link javax.servlet.http.HttpServletRequest#getCharacterEncoding()} 
     * returns a non-null value. Switch this to "true" to enforce the specified 
     * encoding in any case, applying it as default response encoding as well. 
     * <p>Note that the response encoding will only be set on Servlet 2.4+ 
     * containers, since Servlet 2.3 did not provide a facility for setting 
     * a default response encoding. 
     */  
    public void setForceEncoding(boolean forceEncoding) {  
        this.forceEncoding = forceEncoding;  
    }  
  
  
    @Override  
    protected void doFilterInternal(  
            HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)  
            throws ServletException, IOException {  
  
        if (this.encoding != null && (this.forceEncoding || request.getCharacterEncoding() == null)) {  
            request.setCharacterEncoding(this.encoding);  
            if (this.forceEncoding) {  
                response.setCharacterEncoding(this.encoding);  
            }  
        }  
        filterChain.doFilter(request, response);  
    }  
  
}  

这个filter有两个属性,encoding和forceEncoding,我们可以在web.xml文件中来设定这两个属性值。
每次request请求到来执行方法doFilterInternal,首先调用request.getCharacterEncoding(),本质就是从请求header content-type中获取编码值,如果没有,则调用request.setCharacterEncoding(this.encoding)将该filter的encoding值设置为请求体的编码方式,记住该编码方式只对请求体,不针对请求参数。当forceEncoding=true时,不管请求header content-type有没有编码方式,始终将该filter的encoding值设置到request和response中,同样只针对request的请求体。