mybatis的条件test语句当与单个字符比较时报NumberFormatException: For input string问题

错误描述：

<select id="sqlId" resultType="net.test.Statement">
        select *
        from table
        where TRUE
        <if test="type == 'A'">
            AND column = #{column}
        </if>
    </select>

当使用的type为A时，这段便抛出一个NumberFormatExeption的异常，但是如果index为一个数值比如1时就运行正常。
错误：

Caused by: java.lang.NumberFormatException: For input string: "A"
    at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source)
    at java.lang.Double.parseDouble(Unknown Source)
    at org.apache.ibatis.ognl.OgnlOps.doubleValue(OgnlOps.java:248)
    at org.apache.ibatis.ognl.OgnlOps.compareWithConversion(OgnlOps.java:137)
    at org.apache.ibatis.ognl.OgnlOps.isEqual(OgnlOps.java:178)
    at org.apache.ibatis.ognl.OgnlOps.equal(OgnlOps.java:548)
    at org.apache.ibatis.ognl.ASTEq.getValueBody(ASTEq.java:49)
    at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:175)
    at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:213)
    at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:314)
    at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:394)
    at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:435)
    at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:414)
    at org.apache.ibatis.builder.xml.dynamic.ExpressionEvaluator.evaluateBoolean(ExpressionEvaluator.java:17)
    at org.apache.ibatis.builder.xml.dynamic.IfSqlNode.apply(IfSqlNode.java:15)
    at org.apache.ibatis.builder.xml.dynamic.MixedSqlNode.apply(MixedSqlNode.java:14)
    at org.apache.ibatis.builder.xml.dynamic.DynamicSqlSource.getBoundSql(DynamicSqlSource.java:22)
    at org.apache.ibatis.mapping.MappedStatement.getBoundSql(MappedStatement.java:198)
    at org.apache.ibatis.executor.BaseExecutor.createCacheKey(BaseExecutor.java:115)
    at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:90)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:72)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:75)

解决方案：

1.改为：test = "type eq 'A'.toString()"
2.原因是OGNL语法的问题：
这里 'A' 将被认为是 char 类型，但是 'AA' 或者 "A" 将被作为String类型。

所以我们可以用转义：<if test="type == &quot;A&quot;">
3.或者将 <if test="type == 'A'"> 改为 <if test='type == "A"'>。