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
  

• 

• 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<>();

    @Override
    public ParameterHandler createParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
        return new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
    }

    @Override
    public SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType) {
        XMLScriptBuilder builder = new XMLScriptBuilder(configuration, script, parameterType);
        return builder.parseScriptNode();

    }


    @Override
    public 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