一. ORM(Object/Relational Mapper)
1. OR映射---Hibernate基本数据类型
| Hibernate基本类型 |
Java类型 |
标准SQL字段类型 |
| boolean |
boolean, java.lang.Boolean |
BIT |
| yes_no |
boolean, java.lang.Boolean |
CHAR(1) ( 'Y'/'N') |
| true_false |
boolean, java.lang.Boolean |
CHAR(1) ( 'Y'/'N') |
| byte |
byte, java.lang.Byte |
TINYINT |
| short |
short, java.lang.Short |
SMALLINT |
| integer |
int, java.lang.Integer |
INTEGER |
| long |
long, java.lang.Long |
BIGINT |
| float |
float, java.lang.Float |
FLOAT |
| double |
double, java.lang.Double |
DOUBLE |
| big_decimal |
java.math.BigDecimal |
NUMBERIC |
| character |
java.lang.String |
CHAR(1) |
| string |
java.lang.String |
VARCHAR |
| date |
java.util.Date, java.sql.Date |
DATE |
| time |
java.util.Date, java.sql.Time |
TIME |
| timestamp |
java.util.Date, java.sql.TimeStamp |
TIMESTAMP |
| calendar |
java.util.Calendar |
TIMESTAMP |
| calendar_date |
java.util.Calendar |
Date |
| clob |
java.sql.Clob |
CLOB |
| blob |
java.sql.Blob |
BLOB |
| binary |
byte[] |
VARBINARY, BLOB |
| text |
java.lang.String |
CLOB |
| seralizable |
java.io.Serializable |
VARBINARY, BLOB |
| class |
java.lang.Class |
VARCHAR |
| local |
java.util.Locale |
VARCHAR |
| timezone |
java.util.TimeZone |
VARCHAR |
| currency |
java.util.Currency |
VARCHAR |
2. OR映射---实体映射示例
*.hbm.xml, 主体内容包含表/类映射, id映射, 属性字段映射三个部分.示例文件:
<?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>
<class name="cn.thinkmore.hibernate.pojo.Tuser" table="T_user">
<id column="id" name="id" type="java.lang.Integer">
<generator class="increment" />
</id>
<property column="name" name="name" type="java.lang.String"/>
</class>
</hibernate-mapping>
XML文件头定义了文件的编码方式, DTD与Hibernate的版本有关, 上面是使用hibernate 3.x使用的DTD.
3. OR映射---表/类映射
<class name="cn.thinkmore.hibernate.pojo.Tuser" table="T_user">
name: 指定了Java数据封装的POJO类类型.
table: 指定了数据库的表名
4. OR映射---id映射
<id name="id" type="java.lang.Integer" column="id">
<generator class="increment" />
</id>
name: 指定了映射POJO类的属性名,
type: POJO类中属性的数据类型;
column: 数据库表的主键字段;
generator子元素:由其class属性指定主键生成方式:
- assigned: 主键由应用程序产生, 不需要hibernate干预
- identity: 使用数据库的主键生成机制, 如MySQL, DB2、SQL Server的自增主键.
- sequence: 使用数据库的sequence机制, 如Oracle的sequence
- uuid.hex: 由Hibernate基于128位唯一值产生算法, 根据ip, 时间, jvm启动时间, 内部自增量生成十六进制的数值, 编码后成为一个32位长的字符串. 该方法提供了最好的数据库插入性能和数据库平台适应性.
- uuid.string: 与uuid.hex类似, 只是生成的主键没有进行编码, 只有16位长度. 在某些数据库可能出错.
- hilo: 通过hilo算法实现主键生成, 需要额外的数据库表保存主键生成历史状态.
- seqhilo: 与hilo类似, 只是主键历史状态保存在sequence中, 适用于支持sequence的数据库.
- increment: 主键按数值递增, 但如果多个实例同时访问同一个数据库, 各自生成主键,则容易造成主键重复.
- native: 由hibernate根据数据库适配器中的定义, 自动采用identity, hilo, sequence中的一种方式.
- foreign: 外部表的字段作主键.
- select: hibernate 3 中新增的.需要提供一个唯一的标识字段进行二次读取, 以获取触发器生成的主键值, 通过param子元素进行定义, 比如:
<generator class="select">
<param name="key">key_field</param>
</generator>
该方法主要针对遗留系统的改造工程, 一些早期的系统主键依赖于触发器生成. 当数据库insert时, 触发器捕获这一操作, 并为主键赋值, 在插入数据库后, 再次读取某一识别字段读取已经插入的数据, 获取其主键值.
5. OR映射---复合主键映射(composite-id)---实体属性组成主键
复合主键使用<composite-id>将取代id元素, 并具有property属性列表.
<composite-id>
<key-property column="userid" name="userid" type="java.lang.String" />
<key-property column="when" name="when" type="java.sql.Date" />
</composite-id>
复合主键的POJO类需要实现equals和hashcode方法, 可以使用apache commons lang包中的工具类实现(commons-lang.jar), 比如:
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;
...
public String toString(){
return new ToStringBuilder(this)
.append("userid ", getUserid ())
.append("when", getWhen ())
.toString();
}
public boolean equals(Object other){
if(!(other instanceof MyPoJoClass)){
return false;
}
MyPoJoClass castOther=( MyPoJoClass)other;
return new EqualsBuilder()
.appendSuper(super.equals(other))
.append(this.getUserid (),castOther.getUserid() )
.append(this.getWhen (),castOther.getWhen() )
.isEquals();
}
public int hashCode(){
return new HashCodeBuilder()
.appendSuper(super.hashCode() )
.append(getUserid ())
.append(getWhen ())
.toHashCode();
}
装载复合主键的记录时, 考虑把类对应的对象的主键值填充好后作为load的第二个参数.
MyPoJoClass obj = new MyPoJoClass();
obj.setUserid(...);
obj.setWhen(...);
obj=(MyPoJoClass)session.load(MyPoJoClass.class, obj);
6. OR映射---复合主键映射(composite-id)---基于主键类
可以用一个独立的类来描述主键, 示例:
<composite-id name="keyClassProperty" class="MyPoJoClass">
<key-property column="userid" name="userid" type="java.lang.String" />
<key-property column="when" name="when" type="java.sql.Date" />
</composite-id>
此时, 需要定义一个新的类KeyClass来作为主键类, KeyClass实现equals和hashcode方法, 而在POJO中, 使用属性名keyClassProperty来表示主键, 其类类型为KeyClass.
7. OR映射---composite-id其他子节点
composite-id除了key-property子节点外, 还具有可选<key-many-to-one>子节点.完整的节点内容:
<composite-id name="propertyName"
class="ClassName"
unsaved-value="any|none" >
<key-property column="colum_name"
name=" propertyName "
type="type_name" />
...
<key-many-to-one column=" colum_name " calss=" ClassName "
name=" propertyName " />
...
</composite-id>
8. OR映射---属性/字段映射
<property name="name" type="java.lang.String" column="name" />
name: POJO类的属性名,
type: POJO类中属性的数据类型; 如果是字符串,可以省略
column: 数据库中的字段名. 如果和属性同名, 可以省略.
9. OR映射---自定义数据类型 UserType, CompositeUserType接口
hibernate3 中的为: org.hibernate.usertype(hibernate2中为net.sf包)下面的两个接口: UserType 和 CompositeUserType . 它们提供自定义类型的规范, 这里以UserType为例.
package org.hibernate.usertype;
import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.hibernate.HibernateException;
public interface UserType {
/**
* 返回本类型所映射的SQL类型, 返回的是int[]数组. 可以取java.sql.Types中的int静态常量.
* 比如有: public final static int DOUBLE = 8;
*/
public int[] sqlTypes();
/**
* 定义本类型的nullSafeGet() 方法返回的数据的类型
*/
public Class returnedClass();
/**
* 定义两个数据的比较方法, 返回true表示相等, false表示不等.
*/
public boolean equals(Object x, Object y) throws HibernateException;
/**
* Get a hashcode for the instance, consistent with persistence "equality"
*/
public int hashCode(Object x) throws HibernateException;
/**
* 定义从ResultSet中读取数据并转换成自定义类型的方法, 对数据库null应该考虑
* 参数names 包含了当前自定义类型的映射字段名称
*/
public Object nullSafeGet(ResultSet rs, String[] names, Object owner)
throws HibernateException, SQLException;
/**
* Hibernate进行数据保存时被调用的方法
* @param st a JDBC prepared statement
* @param value the object to write, 类型应该是returnedClass()方法返回的Class指定的类型
* @param index statement parameter index
* @throws HibernateException
* @throws SQLException
*/
public void nullSafeSet(PreparedStatement st, Object value, int index)
throws HibernateException, SQLException;
/**
* 自定义的对象复制方法, 用作构造返回对象.
* nullSafeGet方法被调用后, Hibernate获得了自定义数据对象,
* 这个对象成为数据库读出的原始对象, 通过deepCopy方法, Hibernate
* 返回一个复本给用户. 脏数据检查时, 如果两个对象不等(equals方法返回false),
* 就会执行数据库持久化操作.
* @param value the object to be cloned, which may be null
* @return Object a copy
*/
public Object deepCopy(Object value) throws HibernateException;
/**
* Are objects of this type mutable?
* 本类型实例是否可变
* @return boolean
*/
public boolean isMutable();
/**
* 把对象转化为二级缓存中保存. 经常把当前对象对其他对象的引用, 保存为其id值.
* Transform the object into its cacheable representation. At the very least this
* method should perform a deep copy if the type is mutable. That may not be enough
* for some implementations, however; for example, associations must be cached as
* identifier values. (optional operation)
*
* @param value the object to be cached
* @return a cachable representation of the object
* @throws HibernateException
*/
public Serializable disassemble(Object value) throws HibernateException;
/**
* 把二级缓存中获取的数据转换为自定义的对象数据
* Reconstruct an object from the cacheable representation. At the very least this
* method should perform a deep copy if the type is mutable. (optional operation)
*
* @param cached the object to be cached
* @param owner the owner of the cached object
* @return a reconstructed object from the cachable representation
* @throws HibernateException
*/
public Object assemble(Serializable cached, Object owner) throws HibernateException;
/**
* During merge, replace the existing (target) value in the entity we are merging to
* with a new (original) value from the detached entity we are merging. For immutable
* objects, or null values, it is safe to simply return the first parameter. For
* mutable objects, it is safe to return a copy of the first parameter. For objects
* with component values, it might make sense to recursively replace component values.
*
* @param original the value from the detached entity being merged
* @param target the value in the managed entity
* @return the value to be merged
*/
public Object replace(Object original, Object target, Object owner)
throws HibernateException;
}
如果一个用户具有多个email, 可以分别定义多个字段保存, 也可以定义一个子表专门保存, 但都有点大动干戈. 可以考虑用一个字符串字段保存, 相邻的email用一个;隔开. 比如:
package cn.thinkmore.hibernate.pojo;
import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.*;
import org.hibernate.Hibernate;
import org.hibernate.HibernateException;
import org.hibernate.usertype.UserType;
public class EmailList implements UserType {
private static final String SPLITTER = ";";
private static final int[] TYPES = new int[] { Types.VARCHAR };
public Object assemble(Serializable cached, Object owner)
throws HibernateException {
return null;
}
public Object deepCopy(Object value) throws HibernateException {
if (!(value instanceof List)) {
return null;
}
List src = (List) value;
List tar = new ArrayList();
tar.addAll(src);
return tar;
}
public Serializable disassemble(Object value) throws HibernateException {
return null;
}
public boolean equals(Object x, Object y) throws HibernateException {
if (x == y)
return true;
if (x != null && y != null) {
List xList = (List) x;
List yList = (List) y;
if (xList.size() != yList.size())
return false;
for (int i = 0; i < xList.size(); i++) {
String strX = xList.get(i).toString();
String strY = yList.get(i).toString();
if (!strX.equals(strY))
return false;
}
}
return false;
}
public boolean isMutable() {
return false;
}
public Object nullSafeGet(ResultSet rs, String[] names, Object owner)
throws HibernateException, SQLException {
String value = Hibernate.STRING.nullSafeGet(rs, names[0]).toString();
if(null!=value)
return parse(value);
return null;
}
private List parse(String value) {
String[] strs = org.apache.commons.lang.StringUtils.split(value,SPLITTER);
List<String> emails = new ArrayList<String>();
for(int i=0; i<strs.length;i++){
emails.add(strs[i]);
}
return emails;
}
private String assemble(List list) {
StringBuilder sb = new StringBuilder();
int maxIndex = list.size()-1;
for(int i=0; i<maxIndex;i++){
sb.append(list.get(i)).append(SPLITTER);
}
if(0<=maxIndex){
sb.append(list.get(maxIndex));
}
return sb.toString();
}
public void nullSafeSet(PreparedStatement st, Object value, int index)
throws HibernateException, SQLException {
if(null!=value&&(value instanceof List)){
String str = assemble((List)value);
Hibernate.STRING.nullSafeSet(st,str,index);
}else if(null!=value){
Hibernate.STRING.nullSafeSet(st,value.toString(), index);
}else{
Hibernate.STRING.nullSafeSet(st,null, index);
}
}
public Object replace(Object original, Object target, Object owner)
throws HibernateException {
return null;
}
public Class returnedClass() {
return List.class;
}
public int[] sqlTypes() {
return TYPES;
}
public int hashCode(Object x) throws HibernateException {
return 0;
}
}
数据关联关系
数据关联关系在实体的子类里面不会被自动继承.
10. 一对一关联 ----- 主键关联 one-to-one
一对一的主键关联, 指两个表的记录是一对一的关系, 且一个表的主键取为另一个表对应的记录的主键.
<hibernate-mapping>
<class name="cn.thinkmore.hibernate.pojo.Citizen" table="citizen" lazy="true">
<id name="id" column="id">
<generator class="uuid.hex" />
</id>
<property name="name" />
<property name="sex"/>
<property name="idcard" />
<property name="address"/>
<one-to-one name="gene" cascade="all" outer-join="true"
class="cn.thinkmore.hibernate.pojo.Gene" />
</class>
</hibernate-mapping>
name: 属性名
class: java全路径类名
cascade: 是否级连操作, all , none
outer-join: 是否外链接, true/false
<hibernate-mapping>
<class name="cn.thinkmore.hibernate.pojo.Gene" table="gene" lazy="true">
<id name="id" column="id" >
<generator class="foreign">
<param name="property">citizen</param>
</generator>
</id>
<property name="dna" />
<property name="chromosome"/>
<property name="species"/>
<one-to-one name="citizen" constrained="true"
class="cn.thinkmore.hibernate.pojo.Citizen" />
</class>
</hibernate-mapping>
Constrained: 次关联中的约束方.
.....
Session s = HibernateSession3.getSession();
Citizen one = new Citizen();
one.setIdcard("123456789012345678");
one.setName("Mike");
one.setSex("M");
Gene gene = new Gene();
gene.setBloodType("AB");
gene.setDna("Ajodjjd[[joa");
gene.setSpecial("White");
one.setGene(gene);
gene.setCitizen(one);
Transaction trans = s.beginTransaction();
s.saveOrUpdate(one);
trans.commit();
// 两条数据一起被保存, 查询时也会关联查出来.
Query query = s.createQuery("From Citizen");
List list = query.list();
for (int i = 0; i < list.size(); i++) {
one = (Citizen) list.get(i);
if (null == one)
continue;
gene = (Gene) one.getGene();
if (null != gene){
System.out.println(gene.getId()+":"+gene.getSpecial()+":"+gene.getDna());
}
}
11. 单向一对多关联 ----- 唯一外键关联 one-to-many
一个用户可以多个email:
<set name="email" table="emails" cascade="all">
<key column="userid" />
<one-to-many calss="....Email" />
</set>
12. 双向一对多关联
除了在主控方配置一对多, 还要在被控方配置对应的多对一关系:
User:
<set name="email" table="emails" cascade="all" inverse="true">
<key column="userid" />
<one-to-many calss="....Email" />
</set>
Email:
<many-to-one name="user" class=".....User" cascade="none" column="userid" />
再有例子:一个职员(是人的子类)前后可能有多条工作(每次工作是一条记录):
<hibernate-mapping >
<class name="webapp.hibernate.pojo.People" table="people" lazy="false">
<comment>Users may bid for or sell auction items.</comment>
<id name="id">
<generator class="uuid.hex"/>
</id>
<property name="name" />
<property name="idcard" />
<property name="sex"/>
<property name="birth" type="date"/>
<one-to-one name="gene"
cascade="all"
class="webapp.hibernate.pojo.Gene"/>
</class>
</hibernate-mapping>
<hibernate-mapping >
<class name="webapp.hibernate.pojo.Employee" table="people" lazy="false">
<id name="id">
<generator class="uuid.hex"/>
</id>
<property name="name" />
<property name="idcard" />
<property name="sex"/>
<property name="birth" type="date"/>
<one-to-one name="gene"
cascade="all"
class="webapp.hibernate.pojo.Gene"/>
<set name="jobs" table="joblist" cascade="all" inverse="true">
<key column="empid" />
<one-to-many class="webapp.hibernate.pojo.JobList" />
</set>
</class>
</hibernate-mapping>
<hibernate-mapping >
<class name="webapp.hibernate.pojo.JobList" table="joblist" lazy="false">
<id name="id">
<generator class="uuid.hex"/>
</id>
<!-- <property name="userid" column="empid"/> -->
<property name="company" />
<property name="begin" type="date"/>
<property name="end" type="date"/>
<many-to-one name="employee" class="webapp.hibernate.pojo.Employee" cascade="none" column="empid" />
</class>
</hibernate-mapping>
public static void testOne2Many() {
Session s = HibernateSession3.getSession();
Employee e = new Employee();
e.setName("一对多");
e.setIdcard("123456789012345678");
e.setBirth(new java.sql.Date(System.currentTimeMillis()-24L*3600*1000*365*25));
JobList job1 = new JobList();
job1.setEmployee(e);
job1.setCompany("A gongsi");
job1.setBegin(new java.sql.Date(System.currentTimeMillis()-24L*3600*1000*365*5));
job1.setEnd(new java.sql.Date(System.currentTimeMillis()-24L*3600*1000*365*4));
JobList job2 = new JobList();
job2.setEmployee(e);
job2.setCompany("B gongsi");
job2.setBegin(new java.sql.Date(System.currentTimeMillis()-24L*3600*1000*365*4));
job2.setEnd(new java.sql.Date(System.currentTimeMillis()-24L*3600*1000*365*2));
Set<JobList> jobs = new HashSet<JobList>();
jobs.add(job1);
jobs.add(job2);
e.setJobs(jobs);
Transaction trans = s.beginTransaction();
// 两个表的数据一起被保存, 查询时也会关联查出来.
s.saveOrUpdate(e);
trans.commit();
Query query = s.createQuery("From Employee");
List list = query.list();
for (int i = 0; i < list.size(); i++) {
Employee one = (Employee) list.get(i);
if (null == one)
continue;
System.out.println(one.getName()+":"+one.getBirth()+":");
Set joblist = one.getJobs();
for(Object o:joblist){
JobList j = (JobList)o;
System.out.println("\t工作:"+j.getCompany()+":"+j.getBegin()+":"+j.getEnd());
}
System.out.println("---------------------------------------");
}
}
13. 双向多对多关联
一个用户可以在银行有多个帐号
User:
<class name="webapp.hibernate.pojo.MoneyUser" table="people" lazy="false">
<id name="id">
<generator class="uuid.hex"/>
</id>
<property name="name" />
<property name="idcard" />
<property name="sex"/>
<property name="birth" type="date"/>
<one-to-one name="gene"
cascade="all"
class="webapp.hibernate.pojo.Gene"/>
<set name="banks" table="bankuser" cascade="none" >
<key column="userid" />
<many-to-many class="webapp.hibernate.pojo.Bank" column="bankid" />
</set>
</class>
Bank:
<class name="webapp.hibernate.pojo.Bank" table="bank" lazy="false">
<comment>Users may bid for or sell auction items.</comment>
<id name="id">
<generator class="uuid.hex"/>
</id>
<property name="bankname" />
<property name="type"/>
<property name="createday" type="date"/>
<set name="cutomers" table="bankuser" cascade="none" >
<key column="bankid" />
<many-to-many class="webapp.hibernate.pojo.MoneyUser" column="userid" />
</set>
</class>
public static void testMany2Many() {
Session s = HibernateSession3.getSession();
Iterator<MoneyUser> itor =(Iterator<MoneyUser>)s.createQuery("FROM MoneyUser").iterate();
while(itor.hasNext()){
MoneyUser moneyUser = itor.next();
Set banks = moneyUser.getBanks();
Iterator<Bank> bankItor = banks.iterator();
while(bankItor.hasNext()){
Bank bank = bankItor.next();
System.out.println(moneyUser.getName()+" "+bank.getBankname());
}
}
}
public static void testMany2Many2() {
Session s = HibernateSession3.getSession();
Iterator<Bank> itor = s.createQuery("FROM Bank").iterate();
while(itor.hasNext()){
Bank bank = itor.next();
Set customers = bank.getCutomers();
Iterator<MoneyUser> customerItor = customers.iterator();
while(customerItor.hasNext()){
MoneyUser moneyUser = customerItor.next();
System.out.println(bank.getBankname()+" "+moneyUser.getName());
}
}
}
本文转自linzheng 51CTO博客，原文链接:http://blog.51cto.com/linzheng/1080830
