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场景：高并发情况下mybatis 动态sql 解析 锁问题优化

• 优化前 并发测试 XMLLanguageDriver 类 的 createSqlSource 方法有锁 而且 每次执行时都会走该方法
  

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• 优化前 ： 线程有Block
  

• 优化后的 LanguageDriver

public class CustomXMLLanguageDriver implements LanguageDriver {private final Map<String, SqlSource> sqlSourceCache = new ConcurrentHashMap<>();@Overridepublic ParameterHandler createParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {return new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);}@Overridepublic SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType) {XMLScriptBuilder builder = new XMLScriptBuilder(configuration, script, parameterType);return builder.parseScriptNode();}@Overridepublic SqlSource createSqlSource(Configuration configuration, String script, Class<?> parameterType) {if (script.startsWith("<script>")) {SqlSource cachedSqlSource = sqlSourceCache.get(script);if (cachedSqlSource != null) {return cachedSqlSource;}XPathParser parser = new XPathParser(script, false, configuration.getVariables(), new XMLMapperEntityResolver());SqlSource sqlSource = this.createSqlSource(configuration, parser.evalNode("/script"), parameterType);sqlSourceCache.put(script, sqlSource);return  sqlSource;} else {script = PropertyParser.parse(script, configuration.getVariables());TextSqlNode textSqlNode = new TextSqlNode(script);return (SqlSource) (textSqlNode.isDynamic() ? new DynamicSqlSource(configuration, textSqlNode) : new RawSqlSource(configuration, script, parameterType));}}
}

优化后使用相同的压测条件 发现线程没有Block 的 而且调用栈 中只有Druid 的 初始化线程池 有Block XMLLanguageDriver Block 消失

• 此时的 线程没有阻塞