mybatis当传入数据类型为Int时并且值为0时,会判断为空字符串

一个小bug，不过可以调一下mybatis的逻辑，首先加日志打印一下mybatis的日志

• log4j2.xml，日志输出有点儿多

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="OFF">
    <appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
        </Console>
    </appenders>
    <loggers>
        <logger name="log4j.logger.noModule" level="fatal" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.org.mybatis.jpetstore" level="trace" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.com.opensymphony.xwork2" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.com.ibatis" level="trace" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.com.ibatis.common.jdbc.SimpleDataSource" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.com.ibatis.common.jdbc.ScriptRunner" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.com.ibatis.sqlmap.engine.impl.SqlMapClientDelegate" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.org.mybatis" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.java.sql" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.java.sql.Connection" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.java.sql.Statement" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.java.sql.PreparedStatement" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <logger name="log4j.logger.java.sql.ResultSet" level="debug" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
        <root level="trace">
            <appender-ref ref="Console"/>
        </root>
    </loggers>
</configuration>

• 调试
  IfSqlNode里面会计算test表达式的值 OgnlOps的equal方法会真正计算，如果 0 != '' 这个表达式，会进入compareWithConversion方法，

case 8:
double dv1 = doubleValue(v1);
double dv2 = doubleValue(v2);
return dv1 == dv2 ? 0 : (dv1 < dv2 ? -1 : 1);

最终把空字符串和0都转为double，然后 0 != ''就是false，直觉上应该是true，因此引发bug

• 结论
  尽量不要出现不同类型直接的比较

来源：oschina

链接：https://my.oschina.net/wuxiaofei/blog/4317074