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SpringMVC之解决中乱码

1、在web.xml中配置一个CharacterEncodingFilter

<!--因为有缓存的关系,解决中文乱码的过滤器必须要配置在所有过滤器的最前面-->
   <filter>
       <filter-name>characterEncodingFilter</filter-name>
       <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
       <init-param>
           <!--encoding的值是固定的,因为它是CharacterEncodingFilter中的一个属性-->
           <param-name>encoding</param-name>
           <param-value>UTF-8</param-value>
       </init-param>
   </filter>
   <filter-mapping>
       <filter-name>characterEncodingFilter</filter-name>
       <url-pattern>/*</url-pattern>
   </filter-mapping>

2、CharacterEncodingFilter源码如下

public class CharacterEncodingFilter extends OncePerRequestFilter {
    @Nullable
        // web.xml中<param-value>对应的值
    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(@Nullable String encoding) {
        this.encoding = encoding;
    }
 
    @Nullable
    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);
    }
}