关于hibernate反向生成实体类的问题-没有主键的表映射

问题描述：在使用hibernate反向工具的时候，生成的无主键实体类，在查询时结果为空的问题

特注：（本篇文章是针对于那些使用的Spring+Springmvc+hibernate开发框架的同学们的）

通常情况下，使用hibernate反向工具的时候，系统并不会提示你有哪几个表无主键，而是直接将无主键的对应表对应生成两个class文件（分别是xxx.class和xxxid.class  [xxx : 对应的表名]），xxx.class中会给你无主键的表定义一个唯一的Id，然后通过映射文件将表中的所有字段整合为一个复合主键以供hibernate使用。

1.xxx.class示例：

/**
* BlTmsRecipientsTab generated by hbm2java
*/
public class BlTmsRecipientsTab implements java.io.Serializable {

private BlTmsRecipientsTabId id;

public BlTmsRecipientsTab() {
}

public BlTmsRecipientsTab(BlTmsRecipientsTabId id) {
this.id = id;
}

public BlTmsRecipientsTabId getId() {
return this.id;
}

public void setId(BlTmsRecipientsTabId id) {
this.id = id;
}

public String getObjectId(){
return this.id.getObjectId();
}

public void setObjectId(String objectId) {
this.id.setObjectId(objectId);
}

public Date getModiDate() {
return this.id.getModiDate();
}

public void setModiDate(Date modiDate) {
this.id.setModiDate(modiDate);;
}

public String getModiUser() {
return this.id.getModiUser();
}

public void setModiUser(String modiUser) {
this.id.setModiUser(modiUser);;
}

public BigDecimal getDepartmentId() {
return this.id.getDepartmentId();
}

public void setDepartmentId(BigDecimal departmentId) {
this.id.setDepartmentId(departmentId);;
}

public BigDecimal getSubcompanyId() {
return this.id.getSubcompanyId();
}

public void setSubcompanyId(BigDecimal subcompanyId) {
this.id.setSubcompanyId(subcompanyId);;
}

}

2.xxxId.class文件示例：

/**
* BlTmsRecipientsTabId generated by hbm2java
*/
public class BlTmsRecipientsTabId implements java.io.Serializable {

private BigDecimal questId;
private BigDecimal questdispenseId;
private String objectId;
private String enterUser;
private Date enterDate;
private Date modiDate;
private String modiUser;
private BigDecimal departmentId;
private BigDecimal subcompanyId;

public BlTmsRecipientsTabId() {
}

public BigDecimal getQuestId() {
return this.questId;
}

public void setQuestId(BigDecimal questId) {
this.questId = questId;
}

public BigDecimal getQuestdispenseId() {
return this.questdispenseId;
}

public void setQuestdispenseId(BigDecimal questdispenseId) {
this.questdispenseId = questdispenseId;
}

public String getObjectId() {
return this.objectId;
}

public void setObjectId(String objectId) {
this.objectId = objectId;
}

public String getEnterUser() {
return this.enterUser;
}

public void setEnterUser(String enterUser) {
this.enterUser = enterUser;
}

public Date getEnterDate() {
return this.enterDate;
}

public void setEnterDate(Date enterDate) {
this.enterDate = enterDate;
}

public Date getModiDate() {
return this.modiDate;
}

public void setModiDate(Date modiDate) {
this.modiDate = modiDate;
}

public String getModiUser() {
return this.modiUser;
}

public void setModiUser(String modiUser) {
this.modiUser = modiUser;
}

public BigDecimal getDepartmentId() {
return this.departmentId;
}

public void setDepartmentId(BigDecimal departmentId) {
this.departmentId = departmentId;
}

public BigDecimal getSubcompanyId() {
return this.subcompanyId;
}

public void setSubcompanyId(BigDecimal subcompanyId) {
this.subcompanyId = subcompanyId;
}

3.映射文件xxx.hbm.xml

<!-- Generated 2017-4-19 16:22:54 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping>
<class name="com.tms.Beans.BlTmsRecipientsTab" table="BL_TMS_RECIPIENTS_TAB" schema="IFSAPP">
<composite-id name="id" class="com.tms.Beans.BlTmsRecipientsTabId">
<key-property name="questId" type="big_decimal">
<column name="QUEST_ID" precision="22" scale="0" />
</key-property>
<key-property name="questdispenseId" type="big_decimal">
<column name="QUESTDISPENSE_ID" precision="22" scale="0" />
</key-property>
<key-property name="enterUser" type="string">
<column name="ENTER_USER" length="15" />
</key-property>
<key-property name="enterDate" type="date">
<column name="ENTER_DATE" length="7" />
</key-property>
<key-property name="modiDate" type="date">
<column name="MODI_DATE" length="7" />
</key-property>
<key-property name="modiUser" type="string">
<column name="MODI_USER" length="15" />
</key-property>
<key-property name="departmentId" type="big_decimal">
<column name="DEPARTMENT_ID" precision="22" scale="0" />
</key-property>
<key-property name="subcompanyId" type="big_decimal">
<column name="SUBCOMPANY_ID" precision="22" scale="0" />
</key-property>
</composite-id>
</class>
</hibernate-mapping>

那么问题来了，如果你的表中某个字段为空值的话，就会导致复合主键失效，进而导致查询的sql对应不到映射的表，然后就只能返回空值.

所以返回结果为空的原因：因为表中某字段的值为空导致

解决办法：将映射文件中可能出空值的字段从复合主键中移出，

具体操作：1. 将xxx.
4000
hbm.xml文件中可能为空值的字段移出<composite-id>标签，并将移出的<key-property>的统一改为<property>

         示例：

<!-- Generated 2017-4-19 16:22:54 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping>
<class name="com.tms.Beans.BlTmsRecipientsTab" table="BL_TMS_RECIPIENTS_TAB" schema="IFSAPP">
<composite-id name="id" class="com.tms.Beans.BlTmsRecipientsTabId">
<key-property name="questId" type="big_decimal">
<column name="QUEST_ID" precision="22" scale="0" />
</key-property>
<key-property name="questdispenseId" type="big_decimal">
<column name="QUESTDISPENSE_ID" precision="22" scale="0" />
</key-property>
<key-property name="enterUser" type="string">
<column name="ENTER_USER" length="15" />
</key-property>
<key-property name="enterDate" type="date">
<column name="ENTER_DATE" length="7" />
</key-property>
</composite-id>
     /** 修改部份 **/
     <property name="objectId" type="string">
<column name="OBJECT_ID" length="1000" />
</property>
<property name="modiDate" type="date">
<column name="MODI_DATE" length="7" />
</property>
<property name="modiUser" type="string">
<column name="MODI_USER" length="15" />
</property>
<property name="departmentId" type="big_decimal">
<column name="DEPARTMENT_ID" precision="22" scale="0" />
</property>
<property name="subcompanyId" type="big_decimal">
<column name="SUBCOMPANY_ID" precision="22" scale="0" />
</property>
     /**************/
   </class>
</hibernate-mapping>

                

                       2. 在xxx.class文件中加入上一步修改的property对应的变量的get()/set()方法。

然后就ok啦，测试一下，结果返回正常。