最近接触的老项目,总是爱用hibernate,维护起来觉得很麻烦,这里随便总结一下hibernate的特点。
首先:
1.hibernate可以直接对java实例操作,达到数据库的增删改查作用,但是这个实例,只对应一个表。
2.hibernate可以通过编写hql语句,达成自定义SQL查询,但是返回结果,可能是一个map,而无法直接对应成JAVA实例,要自己组装查询结果。
3.hibernate可以通过创建配置文件,配置文件里,定义一个复杂的JAVA实例Class,对应数据库中一个复杂的视图table,并指定在这个复杂视图中,多个表之间的one-to-one, one-to-many, many-to-many关系,和指定哪个字段作为关联条件。而在复杂的java实例中,根据一对一还是一对多的关系,创建其他表的实例作为成员变量,接收其他表的查询结果。既查询一次这个复杂的java实例,就等于关联查询了好多张表。
该文件的命名,一般以XXXX.hbm.xml结尾。
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping auto-import="false">
<class name="com.nstc.cpm.biz.acm.Account" table="V_CPM_BKUNIT_ACCOUNT" lazy="true">
<id name="id" type="java.lang.Integer">
<column name="ACCOUNT_ID" />
<generator class="sequence">
<param name="sequence">S_CPM_BOOK_UNIT</param>
</generator>
</id>
<discriminator column="ACC_CLASS" />
<version name="version" type="java.lang.Integer">
<column name="VERSION_COLUMN" />
</version>
<many-to-one name="customer" class="com.nstc.cpm.biz.acm.Customer" fetch="join" outer-join="true">
<column name="CUST_ID" />
</many-to-one>
<many-to-one name="subject" class="com.nstc.cpm.biz.acm.Subject" fetch="join">
<column name="SUBJECT_ID" length="8" not-null="true" />
</many-to-one>
<many-to-one name="currency" class="com.nstc.cpm.biz.model.BCurrency"
fetch="select" update="false" insert="false">
<column name="CUR_CODE"
not-null="true" />
</many-to-one>
<property name="number" type="java.lang.String" unique="true">
<column name="ACCOUNT_NO" length="32" not-null="true" />
</property>
<one-to-one name="accIntr" class="com.nstc.cpm.biz.acm.DefaultAccIntr" property-ref="accountId"/>
<many-to-one name="type" class="com.nstc.cpm.biz.acm.AccountType" fetch="select" not-null="true">
<column name="TYPE_ID" length="8" />
</many-to-one>
<many-to-one name="bizType" class="com.nstc.cpm.biz.model.BizType" fetch="select">
<column name="BTY_ID" length="6" />
</many-to-one>
<many-to-one name="smartBizType" class="com.nstc.cpm.biz.model.SmartBizType" fetch="select">
<column name="SMART_BTY_ID" />
</many-to-one>
<property name="name" type="java.lang.String">
<column name="ACCOUNT_NAME" length="128" />
</property>
<property name="openDate" type="java.util.Date">
<column name="OPEN_DATE" length="7" />
</property>
<property name="endDate" type="java.util.Date">
<column name="END_DATE" length="7" />
</property>
<property name="interBranchFlag" type="java.lang.Integer">
<column name="INTER_BRANCH_FLAG" />
</property>
<property name="currencyNo" type="java.lang.String">
<column name="CUR_CODE" length="32" not-null="true" />
</property>
<!-- MODIFY BY ZHUQW FOR ZMJT-388 START 20170815 -->
<many-to-one name="branch" class="com.nstc.cpm.biz.model.Branch" fetch="join">
<column name="BRANCH_NO" length="8" not-null="true" />
</many-to-one>
<!-- MODIFY BY ZHUQW FOR ZMJT-388 END 20170815 -->
<property name="balanceDir" type="java.lang.Integer">
<column name="BALANCE_DIR" />
</property>
<property name="state" type="java.lang.Integer">
<column name="ACCOUNT_STATE" />
</property>
<property name="clearDate" type="java.util.Date">
<column name="CLEAR_DATE"/>
</property>
<property name="floorAmount" type="java.lang.Double">
<column name="FLOOR_AMOUNT" />
</property>
<property name="sourceId" type="java.lang.String">
<column name="SOURCE_MARK" length="32" />
</property>
<property name="thirdCustomerId" type="java.lang.Integer">
<column name="THIRD_CUSTOM_ID" />
</property>
<property name="initBalance" type="java.lang.Double">
<column name="INIT_BALANCE"/>
</property>
<property name="sleepState" type="java.lang.Integer">
<column name="SLEEP_STATE"/>
</property>
<property name="accTxDate" type="java.util.Date">
<column name="ACCOUNT_TX_DATE"/>
</property>
<property name="sleepSDate" type="java.util.Date">
<column name="SLEEP_SDATE"/>
</property>
<property name="sleepEDate" type="java.util.Date">
<column name="SLEEP_EDATE"/>
</property>
<set name="intrSbUnits" inverse="true">
<key>
<column name="CPM_ACCOUNT_ID" not-null="true" />
</key>
<one-to-many class="com.nstc.cpm.biz.acm.StandingBookUnit" />
</set>
<subclass name="com.nstc.cpm.biz.acm.CustomerAccount" discriminator-value="CustomerAccount">
<subclass name="com.nstc.cpm.biz.acm.EntitySettlementAccount" discriminator-value="EntitySettlementAccount">
<subclass name="com.nstc.cpm.biz.acm.DemandDepositAccount" discriminator-value="DemandDepositAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.VirtualSettlementAccount" discriminator-value="VirtualSettlementAccount">
<subclass name="com.nstc.cpm.biz.acm.CustLinkageAccount" discriminator-value="CustLinkageAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.DepositAccount" discriminator-value="DepositAccount">
<subclass name="com.nstc.cpm.biz.acm.FixedDepositAccount" discriminator-value="FixedDepositAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.CallDepositAccount" discriminator-value="CallDepositAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.MarginDepositAccount" discriminator-value="MarginDepositAccount">
<subclass name="com.nstc.cpm.biz.acm.MarginDemandDepositAccount" discriminator-value="MarginDemandDepositAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.MarginFixedDepositAccount" discriminator-value="MarginFixedDepositAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.LoanAccount" discriminator-value="LoanAccount">
<subclass name="com.nstc.cpm.biz.acm.CommonLoanAccount" discriminator-value="CommonLoanAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.SyndicatedLoanAccount" discriminator-value="SyndicatedLoanAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.BankAccount" discriminator-value="BankAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.InsideAccountingAccount" discriminator-value="InsideAccountingAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<subclass name="com.nstc.cpm.biz.acm.OffSheetAccountingAccount" discriminator-value="OffSheetAccountingAccount">
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</subclass>
<sql-delete>
delete from CPM_BOOK_UNIT a where a.ACCOUNT_ID=? AND A.VERSION_COLUMN = ?
</sql-delete>
</class>
</hibernate-mapping>
4.hibernate基于JPA,通过注解的方式,来完成数据库的增删改查。使用这个方式,类的成员属性,都需要加上注解,标识这个成员属性,对应表的哪个字段,是否是主键,是否是关联条件。同样的,实体类新增了成员变量,而改变量不对应表的字段时,也要加上注解,标识该字段与表无关。
在多表关联查询的时候,父类查询结果,持有子类查询结果时,还要在父类中还需要持有子查询类的实体类对象,并添加注解,标识改子查询是one-to-one还是one-to-many类型,如果是one-to-many,就需要持有子表实体类的集合作为成员变量。
以上,是我在项目中,遇到的hibernate几种用法。
下面,我们来说一下mybatis,实际上mybatis主要有两种用法:
1.基于注解的,在dao文件中,定义SQL方法,而在每个自定义的SQL方法上,编写mybatis的注解,来对数据库进行操作。但是缺点是多表关联查询,需要编写的SQL比较复杂,使用注解的方式,会更复杂。所以我们一般不用。
2.基于配置文件,基于配置文件的mybatis用法比较常见,有点是,适合编写复杂,超长的sql语句,而且配套的动态sql子句,用起来很好用。