MyBatis 的 XML 文件中特殊字符的处理方法

<!-- 使用 > 表示大于号，>= 表示大于等于号，< 表示小于号，<= 表示小于等于号， -->
<select id="selectByDateRange" resultType="Order">
    SELECT * FROM orders
    WHERE order_date >= #{startDate}
    AND order_date <= #{endDate}
</select>

<select id="selectByIdsWithCondition" resultType="User">
    SELECT * FROM users
    WHERE id IN
    <foreach collection="ids" item="id" open="(" separator="," close=")">
        #{id}
    </foreach>
    AND status < 3  <!-- 必须转义 -->
    ORDER BY create_time DESC
</select>

<!-- 使用 <![CDATA[ ]]> 包裹 SQL -->
<select id="selectByDateRange" resultType="Order">
    <![CDATA[
    SELECT * FROM orders
    WHERE order_date >= #{startDate}
    AND order_date <= #{endDate}
    ]]>
</select>

<select id="selectByCondition" resultType="User">
    SELECT * FROM users
    WHERE 1=1
    <if test="minAge != null">
        AND age > #{minAge}
    </if>
    <if test="maxAge != null">
        AND age < #{maxAge}
    </if>
    <if test="endTime != null">
        <![CDATA[ AND create_time < #{endTime} ]]>
    </if>
</select>

<select id="selectByType" resultType="User">
    SELECT * FROM users
    <where>
        <choose>
            <when test="type == 'young'">
                AND age < 30
            </when>
            <when test="type == 'middle'">
                <![CDATA[ AND age >= 30 AND age < 50 ]]>
            </when>
            <when test="type == 'senior'">
                AND age >= 50
            </when>
        </choose>
    </where>
</select>

符号	XML实体	描述	    示例
-------------------------------------------
>	>	大于号	    age > 18
>=	>=	大于等于号	age >= 18
<	<	小于号	    age < 30
<=	<	小于等于号	age <= 30
&	&	和号	        name & address
'	&apos;	单引号	    name = &apos;John&apos;
"	&quot;	双引号	    name = &quot;John&quot;

<!-- 在 ${} 中也需要转义 -->
<select id="selectWithDynamicColumn" resultType="map">
    SELECT ${columnName} as value
    FROM ${tableName}
    WHERE ${columnName} < #{threshold}
</select>

<select id="selectByMultipleConditions" resultType="User">
    SELECT * FROM users
    WHERE 
        <!-- 使用 BETWEEN -->
        age BETWEEN #{minAge} AND #{maxAge}
        <!-- 结合小于号条件 -->
        <if test="maxScore != null">
            <![CDATA[ AND score < #{maxScore} ]]>
        </if>
        <!-- 使用转义字符 -->
        AND level < #{maxLevel}
</select>

// Java 工具类：自动转义 XML 特殊字符
public class XmlEscapeUtil {
    public static String escapeSqlForXml(String sql) {
        return sql.replace("&", "&")
                  .replace("<", "<")
                  .replace(">", ">")
                  .replace("\"", "&quot;")
                  .replace("'", "&apos;");
    }
    // 使用示例
    public static void main(String[] args) {
        String sql = "SELECT * FROM users WHERE age < 30 AND status > 0";
        System.out.println(escapeSqlForXml(sql));
        // 输出: SELECT * FROM users WHERE age < 30 AND status > 0
    }
}