在Spring mvc框架中是如何解决从页面传来的字符串的编码问题的呢?
下面我们来看看Spring框架给我们提供过滤器CharacterEncodingFilter。
web.xml 中 添加如下配置:
<filter>
<filter-name>characterEncodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<!-- 字符编码 -->
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
<!-- 是否强制所有请求都使用该字符编码 -->
<init-param>
<param-name>forceEncoding</param-name>
<param-value>true</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
spring mvc 内部提供了CharacterEncodingFilter过滤器,该过滤器有两个参数encoding和forceEncoding。
public class CharacterEncodingFilter extends OncePerRequestFilter {
private String encoding;
private boolean forceRequestEncoding = false;
private boolean forceResponseEncoding = false;
public void setEncoding(String encoding) {
this.encoding = encoding;
}
public void setForceEncoding(boolean forceEncoding) {
this.forceRequestEncoding = forceEncoding;
this.forceResponseEncoding = forceEncoding;
}
@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);
}
......
}
CharacterEncodingFilter 中包含 三个属性 encoding、forceRequestEncoding、forceResponseEncoding。
只要过滤器中配置了forceEncoding 属性,则forceRequestEncoding和forceResponseEncoding 则保持一致,都使用forceEncoding的值。
该方法是过滤器的核心方法。
如果forceRequestEncoding=true,和forceResponseEncoding=true,则request和response都是用配置的encoding。 如果forceRequestEncoding=false, 则判断request.getCharacterEncoding()是否有值,如果有值则使用客户端传过来的编码(例如:charset=utf-8)
request中获取encoding,追踪org.apache.coyoteRequest.java类中getCharacterEncoding() 方法。
从代码中发现,contentType 就是从http请求头中获取 content-type属性。
判断 content-type 中是否包含charset属性。如果存在则解析charset的属性值,并返回。