web.xml还不会配置编码过滤器？

向右看齐 2023-10-18 13:08 87阅读 0赞

## 场景 ##

当出现中文乱码问题，Spring中可以利用CharacterEncodingFilter过滤器解决。

## 实现 ##

打开web.xml

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

验证 filter-class是否添加正确，按住ctrl，鼠标左键悬浮上去，出现链接下划线，并且能定位过去，则没问题。

![Image 1][]![20181227154143991.gif][]

定位过去的源码为：

/*
  * Copyright 2002-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 package org.springframework.web.filter;
 
 import java.io.IOException;
 import javax.servlet.FilterChain;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.springframework.util.Assert;
 
 /**
  * Servlet Filter that allows one to specify a character encoding for requests.
  * This is useful because current browsers typically do not set a character
  * encoding even if specified in the HTML page or form.
  *
  * This filter can either apply its encoding if the request does not already
  * specify an encoding, or enforce this filter's encoding in any case
  * ("forceEncoding"="true"). In the latter case, the encoding will also be
  * applied as default response encoding (although this will usually be overridden
  * by a full content type set in the view).
  *
  * @author Juergen Hoeller
  * @since 15.03.2004
  * @see #setEncoding
  * @see #setForceEncoding
  * @see javax.servlet.http.HttpServletRequest#setCharacterEncoding
  * @see javax.servlet.http.HttpServletResponse#setCharacterEncoding
  */
 public class CharacterEncodingFilter extends OncePerRequestFilter {
 
  private String encoding;
 
  private boolean forceRequestEncoding = false;
 
  private boolean forceResponseEncoding = false;
 
 
  /**
   * Create a default {@code CharacterEncodingFilter},
   * with the encoding to be set via {@link #setEncoding}.
   * @see #setEncoding
   */
  public CharacterEncodingFilter() {
  }
 
  /**
   * Create a {@code CharacterEncodingFilter} for the given encoding.
   * @param encoding the encoding to apply
   * @since 4.2.3
   * @see #setEncoding
   */
  public CharacterEncodingFilter(String encoding) {
   this(encoding, false);
  }
 
  /**
   * Create a {@code CharacterEncodingFilter} for the given encoding.
   * @param encoding the encoding to apply
   * @param forceEncoding whether the specified encoding is supposed to
   * override existing request and response encodings
   * @since 4.2.3
   * @see #setEncoding
   * @see #setForceEncoding
   */
  public CharacterEncodingFilter(String encoding, boolean forceEncoding) {
   this(encoding, forceEncoding, forceEncoding);
  }
 
  /**
   * Create a {@code CharacterEncodingFilter} for the given encoding.
   * @param encoding the encoding to apply
   * @param forceRequestEncoding whether the specified encoding is supposed to
   * override existing request encodings
   * @param forceResponseEncoding whether the specified encoding is supposed to
   * override existing response encodings
   * @since 4.3
   * @see #setEncoding
   * @see #setForceRequestEncoding(boolean)
   * @see #setForceResponseEncoding(boolean)
   */
  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;
  }
 
 
  /**
   * Set the encoding to use for requests. This encoding will be passed into a
   * {@link javax.servlet.http.HttpServletRequest#setCharacterEncoding} call.
   * 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;
  }
 
  /**
   * Return the configured encoding for requests and/or responses
   * @since 4.3
   */
  public String getEncoding() {
   return this.encoding;
  }
 
  /**
   * Set whether the configured {@link #setEncoding encoding} of this filter
   * is supposed to override existing request and response encodings.
   * 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.
   * This is the equivalent to setting both {@link #setForceRequestEncoding(boolean)}
   * and {@link #setForceResponseEncoding(boolean)}.
   * @see #setForceRequestEncoding(boolean)
   * @see #setForceResponseEncoding(boolean)
   */
  public void setForceEncoding(boolean forceEncoding) {
   this.forceRequestEncoding = forceEncoding;
   this.forceResponseEncoding = forceEncoding;
  }
 
  /**
   * Set whether the configured {@link #setEncoding encoding} of this filter
   * is supposed to override existing request encodings.
   * 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.
   * @since 4.3
   */
  public void setForceRequestEncoding(boolean forceRequestEncoding) {
   this.forceRequestEncoding = forceRequestEncoding;
  }
 
  /**
   * Return whether the encoding should be forced on requests
   * @since 4.3
   */
  public boolean isForceRequestEncoding() {
   return this.forceRequestEncoding;
  }
 
  /**
   * Set whether the configured {@link #setEncoding encoding} of this filter
   * is supposed to override existing response encodings.
   * Default is "false", i.e. do not modify the encoding.
   * Switch this to "true" to enforce the specified encoding
   * for responses in any case.
   * @since 4.3
   */
  public void setForceResponseEncoding(boolean forceResponseEncoding) {
   this.forceResponseEncoding = forceResponseEncoding;
  }
 
  /**
   * Return whether the encoding should be forced on responses.
   * @since 4.3
   */
  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);
  }
 
 }

[Image 1]: 
[20181227154143991.gif]: https://img-blog.csdnimg.cn/20181227154143991.gif