mybatis实现条件查询

xml配置

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.trustlife.qec.operation.core.dal.mapper.oms.TemplateElementMapper">
  <resultMap id="BaseResultMap" type="com.trustlife.qec.operation.core.dal.dto.oms.TemplateElementDO">
    <id column="id" jdbcType="INTEGER" property="id" />
    <result column="template_id" jdbcType="VARCHAR" property="templateId" />
    <result column="element_name" jdbcType="VARCHAR" property="elementName" />
    <result column="element_jsonpath" jdbcType="VARCHAR" property="elementJsonpath" />
  </resultMap>
  <sql id="Base_Column_List">
    id, template_id, element_name, element_jsonpath
  </sql>

  <select id="selectByCond" parameterType="com.trustlife.qec.operation.core.dal.dto.oms.TemplateElementDO" resultMap="BaseResultMap">
    select
    <include refid="Base_Column_List"></include>
    from oms.t_template_element
    <where>
      <if test="null != id and '' != id">
        and id=#{id}
      </if>
      <if test="null != templateId and '' != templateId">
        and template_id=#{templateId}
      </if>
      <if test="null != elementName and '' != elementName">
        and element_name =#{elementName}
      </if>
      <if test="null != elementJsonpath and '' != elementJsonpath">
        and element_jsonpath =#{elementJsonpath}
      </if>
    </where>
  </select>
</mapper>

DO类

public class TemplateElementDO implements Serializable {
    private Integer id;

    private String templateId;

    private String elementName;

    private String elementJsonpath;

    private static final long serialVersionUID = 1L;

//省略gettersetter

在XML里面，设置parameterType为对应的DO，通过where标签和if标签来判断对应的DO里面是否有值，如果有值的话，就进行拼接。如果DO里面属性都为null，则查询所有的行。