你知道mybatis一对多查询应该要怎样才能够实现吗?很多刚接触mybatis的朋友对于这个问题都不是太了解，那么希望下面的文章可以帮你解决。
mybatis关联查询实现一对多
场景：
一个项目是查询管理人集合，与此同时，每一个管理人还存在多个出资人，要查询一个管理人列表，每一个管理人又包含了出资人列表，采用mybatis关联查询实现返回数据。
下面是实现的方式：
在实体当中，定义包含出资人集合，并创建get set方法;
public class FundManager extends BaseEntity implements Serializable
{
/** 默认字段，禁止更改 **/
@Fieldmeta(name = "主键", logflag = 0)
private String id;
@Fieldmeta(name = "管理人名称", logflag = 0)
private String name;
@Fieldmeta(name = "管理人注册地址", logflag = 0)
private String reginAdress;
@Fieldmeta(name = "法定代表人（委派代表）", logflag = 0)
private String legalName;
@Fieldmeta(name = "法人是否取得基金从业资格证", logflag = 0)
private Integer legalFq;
@Fieldmeta(name = "风控负责人", logflag = 0)
private String riskName;
@Fieldmeta(name = "风控负责人是否取得基金从业资格证", logflag = 0)
private Integer riskFq;
@Fieldmeta(name = "核心团队", logflag = 0)
private String keyman;
@Fieldmeta(name = "驻青岛人员", logflag = 0)
private String qdman;
@Fieldmeta(name = "是否在中基协备案", logflag = 0)
private Integer record;
@Fieldmeta(name = "累计管理基金数量", logflag = 0)
private Integer fundNum;
@Fieldmeta(name = "累计管理基金总规模", logflag = 0)
private BigDecimal totalFundMoney;
@Fieldmeta(name = "累计投资项目数量", logflag = 0)
private Integer investProjectNum;
@Fieldmeta(name = "累计投资项目总金额", logflag = 0)
private BigDecimal totalProjectMoney;
@Fieldmeta(name = "累计退出项目数量", logflag = 0)
private Integer exitProjectNum;
@Fieldmeta(name = "实现上市退出及收益率的项目数量", logflag = 0)
private Integer listProjectNum;
@Fieldmeta(name = "退出项目的投资总金额", logflag = 0)
private BigDecimal exitProjectMoney;
@Fieldmeta(name = "退出项目的总金额", logflag = 0)
private BigDecimal totalExitMoney;
@Fieldmeta(name = "曾经投资青岛项目数量", logflag = 0)
private Integer investQdNum;
@Fieldmeta(name = "投资青岛项目总金额", logflag = 0)
private BigDecimal totalQdMoney;
@Fieldmeta(name = "成功项目1", logflag = 0)
private String aprojectName;
@Fieldmeta(name = "回报倍数1", logflag = 0)
private BigDecimal amultiplier;
@Fieldmeta(name = "成功项目2", logflag = 0)
private String bprojectName;
@Fieldmeta(name = "回报倍数2", logflag = 0)
private BigDecimal bmultiplier;
@Fieldmeta(name = "成功项目3", logflag = 0)
private String cprojectName;
@Fieldmeta(name = "回报倍数3", logflag = 0)
private BigDecimal cmultiplier;
@Fieldmeta(name = "社会信用代码", logflag = 0)
private String unifiedNumber;
@Fieldmeta(name = "成立时间", logflag = 0)
private Date setupDate;
@Fieldmeta(name = "联系人", logflag = 0)
private String contacts;
@Fieldmeta(name = "联系电话", logflag = 0)
private String contactTel;
@Fieldmeta(name = "管理人AMAC登记号", logflag = 0)
private String amacNumber;
@Fieldmeta(name = "管理人登记时间", logflag = 0)
private Date recordDate;
@Fieldmeta(name = "管理公司认缴注册资本", logflag = 0)
private BigDecimal planAmount;
@Fieldmeta(name = "管理公司实缴资本", logflag = 0)
private BigDecimal amount;
@Fieldmeta(name = "管理员是否新设", logflag = 0)
private Integer isNew;
@Fieldmeta(name = "详细介绍", logflag = 0)
private String information;
@Fieldmeta(name = "GP是否同基金管理人(是or否)", logflag = 0)
private Integer managerIsGp;
@Fieldmeta(name = "是否gp", logflag = 0)
private Integer gpFlage;
@Fieldmeta(name = "申报id", logflag = 0)
private String gpNotifyId;
/** 以下是公共扩展属性（若有较多非共性扩展属性，需定义在子类中） **/
private List
<
Investorinfo > investorinfos;
/** 以下是默认get/set方法，一般情况下禁止更改 **/
/** 注意： **/
/** 1，若使用数据字典翻译，建议增加getXXXXValue方法，页面调用使用xXXXXValue **/
/** 2，若字段用于显示时，存在一些特殊处理逻辑，建议增加getXXXXForView方法，页面调用使用xXXXXForView **/
public void setId(String id)
{
this.id = id;
}
public String getId()
{
return this.id;
}
public void setName(String name)
{
this.name = name;
}
public String getName()
{
return this.name;
}
public void setReginAdress(String reginAdress)
{
this.reginAdress = reginAdress;
}
public String getReginAdress()
{
return this.reginAdress;
}
public void setLegalName(String legalName)
{
this.legalName = legalName;
}
public String getLegalName()
{
return this.legalName;
}
public void setLegalFq(Integer legalFq)
{
this.legalFq = legalFq;
}
public Integer getLegalFq()
{
return this.legalFq;
}
public void setRiskName(String riskName)
{
this.riskName = riskName;
}
public String getRiskName()
{
return this.riskName;
}
public void setRiskFq(Integer riskFq)
{
this.riskFq = riskFq;
}
public Integer getRiskFq()
{
return this.riskFq;
}
public void setKeyman(String keyman)
{
this.keyman = keyman;
}
public String getKeyman()
{
return this.keyman;
}
public void setQdman(String qdman)
{
this.qdman = qdman;
}
public String getQdman()
{
return this.qdman;
}
public void setRecord(Integer record)
{
this.record = record;
}
public Integer getRecord()
{
return this.record;
}
public void setFundNum(Integer fundNum)
{
this.fundNum = fundNum;
}
public Integer getFundNum()
{
return this.fundNum;
}
public void setTotalFundMoney(BigDecimal totalFundMoney)
{
this.totalFundMoney = totalFundMoney;
}
public BigDecimal getTotalFundMoney()
{
return this.totalFundMoney;
}
public void setInvestProjectNum(Integer investProjectNum)
{
this.investProjectNum = investProjectNum;
}
public Integer getInvestProjectNum()
{
return this.investProjectNum;
}
public void setTotalProjectMoney(BigDecimal totalProjectMoney)
{
this.totalProjectMoney = totalProjectMoney;
}
public BigDecimal getTotalProjectMoney()
{
return this.totalProjectMoney;
}
public void setExitProjectNum(Integer exitProjectNum)
{
this.exitProjectNum = exitProjectNum;
}
public Integer getExitProjectNum()
{
return this.exitProjectNum;
}
public void setListProjectNum(Integer listProjectNum)
{
this.listProjectNum = listProjectNum;
}
public Integer getListProjectNum()
{
return this.listProjectNum;
}
public void setExitProjectMoney(BigDecimal exitProjectMoney)
{
this.exitProjectMoney = exitProjectMoney;
}
public BigDecimal getExitProjectMoney()
{
return this.exitProjectMoney;
}
public void setTotalExitMoney(BigDecimal totalExitMoney)
{
this.totalExitMoney = totalExitMoney;
}
public BigDecimal getTotalExitMoney()
{
return this.totalExitMoney;
}
public void setInvestQdNum(Integer investQdNum)
{
this.investQdNum = investQdNum;
}
public Integer getInvestQdNum()
{
return this.investQdNum;
}
public void setTotalQdMoney(BigDecimal totalQdMoney)
{
this.totalQdMoney = totalQdMoney;
}
public BigDecimal getTotalQdMoney()
{
return this.totalQdMoney;
}
public void setAprojectName(String aprojectName)
{
this.aprojectName = aprojectName;
}
public String getAprojectName()
{
return this.aprojectName;
}
public void setAmultiplier(BigDecimal amultiplier)
{
this.amultiplier = amultiplier;
}
public BigDecimal getAmultiplier()
{
return this.amultiplier;
}
public void setBprojectName(String bprojectName)
{
this.bprojectName = bprojectName;
}
public String getBprojectName()
{
return this.bprojectName;
}
public void setBmultiplier(BigDecimal bmultiplier)
{
this.bmultiplier = bmultiplier;
}
public BigDecimal getBmultiplier()
{
return this.bmultiplier;
}
public void setCprojectName(String cprojectName)
{
this.cprojectName = cprojectName;
}
public String getCprojectName()
{
return this.cprojectName;
}
public void setCmultiplier(BigDecimal cmultiplier)
{
this.cmultiplier = cmultiplier;
}
public BigDecimal getCmultiplier()
{
return this.cmultiplier;
}
public void setUnifiedNumber(String unifiedNumber)
{
this.unifiedNumber = unifiedNumber;
}
public String getUnifiedNumber()
{
return this.unifiedNumber;
}
public void setSetupDate(Date setupDate)
{
this.setupDate = setupDate;
}
public Date getSetupDate()
{
return this.setupDate;
}
public void setContacts(String contacts)
{
this.contacts = contacts;
}
public String getContacts()
{
return this.contacts;
}
public void setContactTel(String contactTel)
{
this.contactTel = contactTel;
}
public String getContactTel()
{
return this.contactTel;
}
public void setAmacNumber(String amacNumber)
{
this.amacNumber = amacNumber;
}
public String getAmacNumber()
{
return this.amacNumber;
}
public void setRecordDate(Date recordDate)
{
this.recordDate = recordDate;
}
public Date getRecordDate()
{
return this.recordDate;
}
public void setPlanAmount(BigDecimal planAmount)
{
this.planAmount = planAmount;
}
public BigDecimal getPlanAmount()
{
return this.planAmount;
}
public void setAmount(BigDecimal amount)
{
this.amount = amount;
}
public BigDecimal getAmount()
{
return this.amount;
}
public void setIsNew(Integer isNew)
{
this.isNew = isNew;
}
public Integer getIsNew()
{
return this.isNew;
}
public void setInformation(String information)
{
this.information = information;
}
public String getInformation()
{
return this.information;
}
public void setManagerIsGp(Integer managerIsGp)
{
this.managerIsGp = managerIsGp;
}
public Integer getManagerIsGp()
{
return this.managerIsGp;
}
public void setGpFlage(Integer gpFlage)
{
this.gpFlage = gpFlage;
}
public Integer getGpFlage()
{
return this.gpFlage;
}
public String getGpNotifyId()
{
return gpNotifyId;
}
public void setGpNotifyId(String gpNotifyId)
{
this.gpNotifyId = gpNotifyId;
}
/** 扩展get/set方法 **/
public List
<
Investorinfo > getInvestorinfos()
{
return investorinfos;
}
public void setInvestorinfos(List <
Investorinfo > investorinfos)
{
this.investorinfos = investorinfos;
}
}mybatis.xml文件当中实现
定义基本查询语句查询管理人集合，返回resultMap结果集，在resultMap返回结果当中，进行关联关系映射查询，collection实现一对多查询;
在这当中id标签是查询fundManager的id在管理时的别名和关联字短。
例如：on t.id=s.id
在collection标签当中通过select来指定关联的查询语句，但是这次关联的2个查询分别属于不同的xml文件，那么，这个时候要怎样实现在一个mapper.xml文件当中引用另外一个mapper.xml文件的查询语句呢。
采用命名空间加.id属性对应的名方式
fundManagerMapper.xml
<!-- #######【开始】扩展代码区，可自由改动。####### -->
<resultMap id="ResultMapWithInvestor" type="com.qk.gpportal.core.fundmanager.entity.FundManager" extends="BaseResultMap">
<id property="id" column="id"/>
<collection property="investorinfos" ofType="com.qk.gpportal.core.investorinfo.entity.Investorinfo" column="id" select="com.qk.gpportal.core.investorinfo.dao.InvestorinfoMapper.getInvestors"></collection>
</resultMap>
<select id="getFundManagerBygpNotifyId" parameterType="java.lang.String" resultMap="ResultMapWithInvestor">
select
<include refid="Columns"/>
FROM g_fund_manager WHERE gp_notify_id= #{gpNotifyId,jdbcType=VARCHAR}
</select>
<!-- #######【结束】扩展代码区，可自由改动。####### -->investorinfoMapper.xml id的名字通过在fundmanagerMapper.xml文件当中表空间方式.id名称方式引用，能够实现不同.xml方法之间的引用。
<select id="getInvestors" resultMap="BaseResultMap" parameterType="java.lang.String">
select
<include refid="Columns"/>
from g_investorinfo where fund_manager_id = #{id}
</select>关于mybatis实现一对多查询的方式就给你介绍到这里了，你还想了解更多相关知识吗?请继续关注本站来了解吧!更多java常见问题及解决方法可以为你分享哦。
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