Mybatis的mapper.xml中if标签test判断的用法说明

<if test=' testString != null and testString == "A" '>
   AND 表字段 = #{testString}
</if>

<if test=" testString != null and testString == 'A'.toString() ">
　　AND 表字段 = #{testString}
</if>

<if test="xxx !=null and xxx !=''">

<if test="xxx !=null and xxx !='' or xxx == 0">

<if test="@完整的包名类名@方法名(传参)">

<if test="@com.xxx.util.MybatisTestUtil@isNotEmpty(obj)">

import java.util.Collection;
import java.util.Map;
/**
 * @description: mybatis的<if test="">标签中使用的非空判断工具类
 *      使用方式：<if test="@com.xxx.xxx.util.MybatisTsetUtil@isNotEmpty(obj)">
 * @author: singleDog
 * @date: 2020/7/20
 */
public class MybatisTestUtil {
    public static boolean isEmpty(Object o) {
        if (o == null) {
            return true;
        }
        if (o instanceof String) {
            return ((String) o).trim().length() == 0;
        } else if (o instanceof Collection) {
            return ((Collection) o).isEmpty();
        } else if (o instanceof Map) {
            return ((Map) o).isEmpty();
        } else if (o.getClass().isArray()) {
            return ((Object[]) o).length == 0;
        } else {
            return false;
        }
    }
    public static boolean isNotEmpty(Object o) {
        return !isEmpty(o);
    }
}

<if test="list.contains(xxx)">
    //...
</if>

<!--包含-->
<if test="list.contains('示例元素'.toString())">
    //...
</if>

<!--不包含-->
<if test="!list.contains('示例元素'.toString())">
    //...
</if>

map.put("startNum",(page.getPageNum()-1)*page.getNumPerPage());
map.put("pageSize",page.getNumPerPage());

<if test="startNum != null  and startNum != '' ">
       LIMIT #{startNum},#{pageSize}
</if>

<if test="startNum != null">
       LIMIT #{startNum},#{pageSize}
</if>

map.put("uploadFlag",upload.getUploadFlag());

<if test="uploadFlag=='1'.toString()">
     and pw.id in (select pw_id from t_contract_upload)
</if>

<if test='uploadFlag=="2" '>
     and pw.id in (select pw_id from t_contract_upload)
</if>