编写敏感词过滤器
敏感词过滤器用来过滤掉字符串或文本中的敏感词汇！
package com.nowcoder.community.util;
import org.apache.commons.lang3.CharUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
@Component
public class SensitiveFilter {
private static final Logger logger = LoggerFactory.getLogger(SensitiveFilter.class);
// 替换符（用来替换掉敏感词）
private static final String REPLACEMENT = "***";
// 根节点
private TrieNode rootNode = new TrieNode();
@PostConstruct // spring容器在实例化bean之后，调用这个初始化方法(即在构造器之后被调用)
public void init() {
try (
InputStream is = this.getClass().getClassLoader().getResourceAsStream("sensitive-words.txt");
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
) {
String keyword;
while ((keyword = reader.readLine()) != null) {
// 添加到前缀树
this.addKeyword(keyword);
}
} catch (IOException e) {
logger.error("加载敏感词文件失败: " + e.getMessage());
}
}
// 将一个敏感词添加到前缀树中
private void addKeyword(String keyword) {
TrieNode tempNode = rootNode;
for (int i = 0; i < keyword.length(); i++) {
char c = keyword.charAt(i);
TrieNode subNode = tempNode.getSubNode(c);
if (subNode == null) {
// 初始化子节点
subNode = new TrieNode();
tempNode.addSubNode(c, subNode);
}
// 指向子节点,进入下一轮循环
tempNode = subNode;
// 设置结束标识
if (i == keyword.length() - 1) {
tempNode.setKeywordEnd(true);
}
}
}
/**
* 过滤敏感词
*
* @param text 待过滤的文本
* @return 过滤后的文本
*/
public String filter(String text) {
if (StringUtils.isBlank(text)) {
return null;
}
// 指针1
TrieNode tempNode = rootNode;
// 指针2
int begin = 0;
// 指针3
int position = 0;
// 结果
StringBuilder sb = new StringBuilder();
while (position < text.length()) {
char c = text.charAt(position);
// 跳过符号
if (isSymbol(c)) {
// 若指针1处于根节点,将此符号计入结果,让指针2向下走一步
if (tempNode == rootNode) {
sb.append(c);
begin++;
}
// 无论符号在开头或中间,指针3都向下走一步
position++;
continue;
}
// 检查下级节点
tempNode = tempNode.getSubNode(c);
if (tempNode == null) {
// 以begin开头的字符串不是敏感词
sb.append(text.charAt(begin));
// 进入下一个位置
position = ++begin;
// 重新指向根节点
tempNode = rootNode;
} else if (tempNode.isKeywordEnd()) {
// 发现敏感词,将begin~position字符串替换掉
sb.append(REPLACEMENT);
// 进入下一个位置
begin = ++position;
// 重新指向根节点
tempNode = rootNode;
} else {
// 检查下一个字符
position++;
}
}
// 将最后一批字符计入结果
sb.append(text.substring(begin));
return sb.toString();
}
// 判断是否为符号
private boolean isSymbol(Character c) {
// 0x2E80~0x9FFF 是东亚文字范围
return !CharUtils.isAsciiAlphanumeric(c) && (c < 0x2E80 || c > 0x9FFF);
}
// 前缀树
private class TrieNode {
// 关键词结束标识
private boolean isKeywordEnd = false;
// 子节点(key是下级字符,value是下级节点)
private Map<Character, TrieNode> subNodes = new HashMap<>();
public boolean isKeywordEnd() {
return isKeywordEnd;
}
public void setKeywordEnd(boolean keywordEnd) {
isKeywordEnd = keywordEnd;
}
// 添加子节点
public void addSubNode(Character c, TrieNode node) {
subNodes.put(c, node);
}
// 获取子节点
public TrieNode getSubNode(Character c) {
return subNodes.get(c);
}
}
}
测试敏感词过滤器
单元测试类编写
package com.nowcoder.community;
import com.nowcoder.community.util.SensitiveFilter;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(classes = CommunityApplication.class)
public class SensitiveTests {
@Autowired
private SensitiveFilter sensitiveFilter;
@Test
public void testSensitiveFilter() {
String text = "这里可以赌博,可以嫖娼,可以吸毒,可以开票,哈哈哈!";
text = sensitiveFilter.filter(text);
System.out.println(text);
text = "这里可以☆赌☆博☆,可以☆嫖☆娼☆,可以☆吸☆毒☆,可以☆开☆票☆,哈哈哈!";
text = sensitiveFilter.filter(text);
System.out.println(text);
}
}
测试结果
. ____ _ __ _ _ /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.1.5.RELEASE) 2020-03-22 09:54:32,698 INFO [main] c.n.c.SensitiveTests [StartupInfoLogger.java:50] Starting SensitiveTests on lzph-pc with PID 8344 (started by admin in E:\nowcoder\nowcoder-workspace\community-3.1) 2020-03-22 09:54:32,724 DEBUG [main] c.n.c.SensitiveTests [StartupInfoLogger.java:53] Running with Spring Boot v2.1.5.RELEASE, Spring v5.1.7.RELEASE 2020-03-22 09:54:32,727 INFO [main] c.n.c.SensitiveTests [SpringApplication.java:675] No active profile set, falling back to default profiles: default 2020-03-22 09:54:43,864 INFO [main] o.s.s.c.ThreadPoolTaskExecutor [ExecutorConfigurationSupport.java:171] Initializing ExecutorService 'applicationTaskExecutor' 2020-03-22 09:54:44,702 INFO [main] o.s.b.a.w.s.WelcomePageHandlerMapping [WelcomePageHandlerMapping.java:61] Adding welcome page template: index 2020-03-22 09:54:45,895 INFO [main] c.n.c.SensitiveTests [StartupInfoLogger.java:59] Started SensitiveTests in 15.275 seconds (JVM running for 18.752) 这里可以***,可以***,可以***,可以***,哈哈哈! 这里可以☆***☆,可以☆***☆,可以☆***☆,可以☆***☆,哈哈哈! 2020-03-22 09:54:47,377 INFO [Thread-3] o.s.s.c.ThreadPoolTaskExecutor [ExecutorConfigurationSupport.java:208] Shutting down ExecutorService 'applicationTaskExecutor'
参考资料
示例中用到的相关数据结构的知识点：前缀树（字典树），参考如下文章：
https://www.cnblogs.com/luosongchao/p/3239521.html