我正在使用mybatis，遇到关联查询问题，请先看一下表结构。
DROP TABLE IF EXISTS `comp_items_spec`;
CREATE TABLE `comp_items_spec` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`comp_id` int(11) NOT NULL,
`content_type_id` int(11) NOT NULL,
`in_list_flag` char(1) DEFAULT NULL,
`label` varchar(200) DEFAULT NULL,
`static_flag` char(1) DEFAULT NULL,
`ext1_name` varchar(200) DEFAULT NULL,
`ext1_value` text,
`ext2_name` varchar(200) DEFAULT NULL,
`ext2_value` text,
`ext3_name` varchar(200) DEFAULT NULL,
`ext3_value` text,
`ext4_name` varchar(200) DEFAULT NULL,
`ext4_value` text,
`ext5_name` varchar(200) DEFAULT NULL,
`ext5_value` text,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=47 DEFAULT CHARSET=latin1;
/*Data for the table `comp_items_spec` */
insert into `comp_items_spec`(`id`,`comp_id`,`content_type_id`,`in_list_flag`,`label`,`static_flag`,`ext1_name`,`ext1_value`,`ext2_name`,`ext2_value`,`ext3_name`,`ext3_value`,`ext4_name`,`ext4_value`,`ext5_name`,`ext5_value`) values (43,22,1,'\0','description','Y','description','description1......',NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL),(44,22,3,'\0','static image','Y',NULL,'http://img3.cache.netease.com/cnews/2012/12/6/20121206092637ba11c.jpg',NULL,'501',NULL,'425',NULL,NULL,NULL,NULL);
/*Table structure for table `components_spec` */
DROP TABLE IF EXISTS `components_spec`;
CREATE TABLE `components_spec` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(200) DEFAULT NULL,
`show_latest_num` int(11) DEFAULT NULL,
`more_link_url` varchar(200) DEFAULT NULL,
`more_link_flag` char(1) DEFAULT NULL,
`open_in_new_flag` char(1) DEFAULT NULL,
`create_date` datetime DEFAULT NULL,
`update_date` datetime DEFAULT NULL,
`creator_sso` varchar(20) DEFAULT NULL,
`updator_sso` varchar(20) DEFAULT NULL,
KEY `id` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=23 DEFAULT CHARSET=latin1;
/*Data for the table `components_spec` */
insert into `components_spec`(`id`,`name`,`show_latest_num`,`more_link_url`,`more_link_flag`,`open_in_new_flag`,`create_date`,`update_date`,`creator_sso`,`updator_sso`) values (22,'Banner',5,'more.blog.ge.com','Y','Y','2012-12-08 21:30:58','2012-12-08 21:30:58','502156886','502156886');
components_spec和comp_items_spec之间的关系是1：N，comp_items_spec有两种数据，动态项和静态项，它们与列static_flag不同，它是static_flag ='N'时的动态项，我还定义了bean ComponentSpec和CompItemSpec映射实体。请参阅下面的源代码：
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class ComponentSpec {
private int id;
private String name;
private int showLatestNum;
private String moreLinkUrl;
private char moreLinkFlag;
private char openInNewFlag;
private Date createDate;
private Date updateDate;
private String creatorSSO;
private String updatorSSO;
private List<CompItemSpec> staticItemSpecList =new ArrayList<CompItemSpec>();
private List<CompItemSpec> dynamicItemSpecList =new ArrayList<CompItemSpec>();
public Date getCreateDate() {
return createDate;
}
public void setCreateDate(Date createDate) {
this.createDate = createDate;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public char getMoreLinkFlag() {
return moreLinkFlag;
}
public void setMoreLinkFlag(char moreLinkFlag) {
this.moreLinkFlag = moreLinkFlag;
}
public String getMoreLinkUrl() {
return moreLinkUrl;
}
public void setMoreLinkUrl(String moreLinkUrl) {
this.moreLinkUrl = moreLinkUrl;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getShowLatestNum() {
return showLatestNum;
}
public void setShowLatestNum(int showLatestNum) {
this.showLatestNum = showLatestNum;
}
public Date getUpdateDate() {
return updateDate;
}
public void setUpdateDate(Date updateDate) {
this.updateDate = updateDate;
}
public char getOpenInNewFlag() {
return openInNewFlag;
}
public void setOpenInNewFlag(char openInNewFlag) {
this.openInNewFlag = openInNewFlag;
}
public List<CompItemSpec> getStaticItemSpecList() {
return staticItemSpecList;
}
public void addStaticItemSpec(CompItemSpec compStaticItemSpec){
getStaticItemSpecList().add(compStaticItemSpec);
compStaticItemSpec.setComponentSpec(this);
}
public List<CompItemSpec> getDynamicItemSpecList() {
return dynamicItemSpecList;
}
public void addDynamicItemSpec(CompItemSpec dynamicItemSpec){
getDynamicItemSpecList().add(dynamicItemSpec);
dynamicItemSpec.setComponentSpec(this);
}
public String getCreatorSSO() {
return creatorSSO;
}
public void setCreatorSSO(String creatorSSO) {
this.creatorSSO = creatorSSO;
}
public String getUpdatorSSO() {
return updatorSSO;
}
public void setUpdatorSSO(String updatorSSO) {
this.updatorSSO = updatorSSO;
}
}
public class CompItemSpec {
private int id;
private int compId;
private int contentTypeId;
private char inListFlag;
private char staticFlag;
private String label;
private String ext1Name;
private String ext1Value;
private String ext2Name;
private String ext2Value;
private String ext3Name;
private String ext3Value;
private String ext4Name;
private String ext4Value;
private String ext5Name;
private String ext5Value;
private ComponentSpec componentSpec;
public int getCompId() {
return compId;
}
public void setCompId(int compId) {
this.compId = compId;
}
public String getExt1Name() {
return ext1Name;
}
public void setExt1Name(String ext1Name) {
this.ext1Name = ext1Name;
}
public String getExt1Value() {
return ext1Value;
}
public void setExt1Value(String ext1Value) {
this.ext1Value = ext1Value;
}
public String getExt2Name() {
return ext2Name;
}
public void setExt2Name(String ext2Name) {
this.ext2Name = ext2Name;
}
public String getExt2Value() {
return ext2Value;
}
public void setExt2Value(String ext2Value) {
this.ext2Value = ext2Value;
}
public String getExt3Name() {
return ext3Name;
}
public void setExt3Name(String ext3Name) {
this.ext3Name = ext3Name;
}
public String getExt3Value() {
return ext3Value;
}
public void setExt3Value(String ext3Value) {
this.ext3Value = ext3Value;
}
public String getExt4Name() {
return ext4Name;
}
public void setExt4Name(String ext4Name) {
this.ext4Name = ext4Name;
}
public String getExt4Value() {
return ext4Value;
}
public void setExt4Value(String ext4Value) {
this.ext4Value = ext4Value;
}
public String getExt5Name() {
return ext5Name;
}
public void setExt5Name(String ext5Name) {
this.ext5Name = ext5Name;
}
public String getExt5Value() {
return ext5Value;
}
public void setExt5Value(String ext5Value) {
this.ext5Value = ext5Value;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getContentTypeId() {
return contentTypeId;
}
public void setContentTypeId(int contentTypeId) {
this.contentTypeId = contentTypeId;
}
public char getInListFlag() {
return inListFlag;
}
public void setInListFlag(char inListFlag) {
this.inListFlag = inListFlag;
}
public char getStaticFlag() {
return staticFlag;
}
public void setStaticFlag(char staticFlag) {
this.staticFlag = staticFlag;
}
public String getLabel() {
return label;
}
public void setLabel(String label) {
this.label = label;
}
public ComponentSpec getComponentSpec() {
return componentSpec;
}
public void setComponentSpec(ComponentSpec componentSpec) {
this.componentSpec = componentSpec;
}
}
sqlmap如下所示：
<mapper namespace="com.ge.dao.ComponentSpecMapper">
<resultMap id="componentMap" type="componentSpec">
<id column="id" property="id"/>
<result column="temp_id" property="tempId"/>
<result column="show_latest_num" property="showLatestNum"/>
<result column="more_link_url" property="moreLinkUrl"/>
<result column="more_link_flag" property="moreLinkFlag"/>
<result column="open_in_new_flag" property="openInNewFlag"/>
<result column="update_date" property="updateDate"/>
<result column="create_date" property="createDate"/>
<result column="updator_sso" property="updatorSSO"/>
<result column="creator_sso" property="creatorSSO"/>
<collection property="staticItemSpecList" ofType="itemSpec">
<id column="static_item_id" property="id"/>
<result column="id" property="compId"/>
<result column="static_content_type_id" property="contentTypeId"/>
<result column="static_label" property="label"/>
<result column="static_ext1_value" property="ext1Value"/>
<result column="static_ext2_value" property="ext2Value"/>
<result column="static_ext3_value" property="ext3Value"/>
<result column="static_ext4_value" property="ext4Value"/>
<result column="static_ext5_value" property="ext5Value"/>
</collection>
<collection property="dynamicItemSpecList" ofType="itemSpec">
<id column="dynamic_item_id" property="id"/>
<result column="id" property="compId"/>
<result column="dynamic_content_type_id" property="contentTypeId"/>
<result column="dynamic_in_list_flag" property="inListFlag"/>
<result column="dynamic_label" property="label"/>
<result column="dynamic_ext1_value" property="ext1Value"/>
<result column="dynamic_ext2_value" property="ext2Value"/>
<result column="dynamic_ext3_value" property="ext3Value"/>
<result column="dynamic_ext4_value" property="ext4Value"/>
<result column="dynamic_ext5_value" property="ext5Value"/>
</collection>
</resultMap>
<sql id="compSpecMain">
SELECT
comp.id,
comp.name,
show_latest_num,
more_link_url,
more_link_flag,
open_in_new_flag,
create_date,
update_date,
creator_sso,
updator_sso,
si.id static_item_id,
si.content_type_id static_content_type_id,
si.in_list_flag static_in_list_flag,
si.label static_label,
si.ext1_value static_ext1_value,
si.ext2_value static_ext2_value,
si.ext3_value static_ext3_value,
si.ext4_value static_ext4_value,
si.ext5_value static_ext5_value,
di.id dynamic_item_id,
di.content_type_id dynamic_content_type_id,
di.in_list_flag dynamic_in_list_flag,
di.label dynamic_label,
di.ext1_value dynamic_ext1_value,
di.ext2_value dynamic_ext2_value,
di.ext3_value dynamic_ext3_value,
di.ext4_value dynamic_ext4_value,
di.ext5_value dynamic_ext5_value
FROM components_spec comp
LEFT JOIN comp_items_spec si ON si.comp_id=comp.id AND si.static_flag='Y'
LEFT JOIN comp_items_spec di ON di.comp_id=comp.id AND di.static_flag='N'
</sql>
<select id="selectComponentSpecByID" parameterType="int" resultMap="componentMap">
<include refid="compSpecMain"/>
WHERE
comp.id=#{id}
</select>
<select id="selectComponentSpecByName" parameterType="string" resultMap="componentMap">
<include refid="compSpecMain"/>
WHERE
comp.name like #{name}
</select>
这里的问题是当我执行selectComponentSpecByID查询时，动态项列表应该没有，但实际结果是两个元素，我认为这是结果映射定义的问题，但没有胶水。有什么建议？谢谢。
答案 0 :(得分：1)
最后我自己找到了解决方案，因为当id属性为null时，意味着在结果中没有检索到记录，mybatis仍然比较它们并将它们视为有效结果并将它们放入子列表中，这就是修复它的原因，只需定义Collection元素的notNullColumn，以防止null id。完成！
<resultMap id="componentMap" type="componentSpec">
<id column="id" property="id"/>
<result column="temp_id" property="tempId"/>
<result column="show_latest_num" property="showLatestNum"/>
<result column="more_link_url" property="moreLinkUrl"/>
<result column="more_link_flag" property="moreLinkFlag"/>
<result column="open_in_new_flag" property="openInNewFlag"/>
<result column="update_date" property="updateDate"/>
<result column="create_date" property="createDate"/>
<result column="updator_sso" property="updatorSSO"/>
<result column="creator_sso" property="creatorSSO"/>
<collection property="staticItemSpecList" notNullColumn="static_item_id" ofType="itemSpec">
<id column="static_item_id" property="id"/>
<result column="id" property="compId"/>
<result column="static_content_type_id" property="contentTypeId"/>
<result column="static_label" property="label"/>
<result column="static_ext1_value" property="ext1Value"/>
<result column="static_ext2_value" property="ext2Value"/>
<result column="static_ext3_value" property="ext3Value"/>
<result column="static_ext4_value" property="ext4Value"/>
<result column="static_ext5_value" property="ext5Value"/>
</collection>
<collection property="dynamicItemSpecList" notNullColumn="dynamic_item_id" ofType="itemSpec">
<id column="dynamic_item_id" property="id"/>
<result column="id" property="compId"/>
<result column="dynamic_content_type_id" property="contentTypeId"/>
<result column="dynamic_in_list_flag" property="inListFlag"/>
<result column="dynamic_label" property="label"/>
<result column="dynamic_ext1_value" property="ext1Value"/>
<result column="dynamic_ext2_value" property="ext2Value"/>
<result column="dynamic_ext3_value" property="ext3Value"/>
<result column="dynamic_ext4_value" property="ext4Value"/>
<result column="dynamic_ext5_value" property="ext5Value"/>
</collection>
</resultMap>