添加邮件脱敏规则：

// 123123123@qq.com，将@前4个字符脱敏
12312****@qq.com

代码重写MaskAlgorithm相关方法： 

/** Licensed to the Apache Software Foundation (ASF) under one or more* contributor license agreements.  See the NOTICE file distributed with* this work for additional information regarding copyright ownership.* The ASF licenses this file to You 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.*/import com.google.common.base.Strings;
import org.apache.shardingsphere.mask.algorithm.MaskAlgorithmPropertiesChecker;
import org.apache.shardingsphere.mask.spi.MaskAlgorithm;import java.util.Properties;/*** Mask after special-chars algorithm.*/
public final class MaskBeforeSpecialNCharsAlgorithm implements MaskAlgorithm<Object, String> {private static final String SPECIAL_CHARS = "special-chars";private static final String REPLACE_CHAR = "replace-char";private static final String FIRST_N = "first-n";private String specialChars;private Character replaceChar;private Integer firstN;@Overridepublic void init(final Properties props) {specialChars = createSpecialChars(props);replaceChar = createReplaceChar(props);firstN = createFirstN(props);}private Integer createFirstN(final Properties props) {MaskAlgorithmPropertiesChecker.checkPositiveInteger(props, FIRST_N, this);return Integer.parseInt(props.getProperty(FIRST_N));}private String createSpecialChars(final Properties props) {MaskAlgorithmPropertiesChecker.checkAtLeastOneChar(props, SPECIAL_CHARS, this);return props.getProperty(SPECIAL_CHARS);}private Character createReplaceChar(final Properties props) {MaskAlgorithmPropertiesChecker.checkSingleChar(props, REPLACE_CHAR, this);return props.getProperty(REPLACE_CHAR).charAt(0);}@Overridepublic String mask(final Object plainValue) {String result = null == plainValue ? null : String.valueOf(plainValue);if (Strings.isNullOrEmpty(result)) {return result;}int index = result.contains(specialChars) ? result.indexOf(specialChars) : -1;char[] chars = result.toCharArray();for (int i = index-firstN; i < index; i++) {chars[i] = replaceChar;}return new String(chars);}@Overridepublic String getType() {return "MASK_BEFORE_SPECIAL_N_CHARS";}
}

 pom: 依赖版本5.5.0

        <!-- 相关依赖 --><dependency><groupId>org.apache.shardingsphere</groupId><artifactId>shardingsphere-jdbc</artifactId></dependency><dependency><groupId>org.yaml</groupId><artifactId>snakeyaml</artifactId></dependency><dependency><groupId>org.apache.shardingsphere</groupId><artifactId>shardingsphere-infra-common</artifactId></dependency><dependency><groupId>io.swagger</groupId><artifactId>swagger-annotations</artifactId><version>${swaggerannotations.version}</version></dependency><dependency><groupId>org.apache.shardingsphere</groupId><artifactId>shardingsphere-mask-api</artifactId></dependency><dependency><groupId>org.apache.shardingsphere</groupId><artifactId>shardingsphere-mask-core</artifactId></dependency>

项目中添加如下配置： 

org.apache.shardingsphere.mask.spi.MaskAlgorithm文件中增加脱敏类： 

com.xx.xxx.plugin.MaskBeforeSpecialNCharsAlgorithm

 yml中如下配置：

rules:- !MASKtables:ac_user:columns:password:maskAlgorithm: md5_maskemail:maskAlgorithm: mask_before_special_n_chars_maskphone_number:maskAlgorithm: keep_first_n_last_m_maskmaskAlgorithms:md5_mask:type: MD5mask_before_special_n_chars_mask:type: MASK_BEFORE_SPECIAL_N_CHARSprops:special-chars: '@'replace-char: '*'first-n: 4