hibernate之定制属性访问(field|property|noop)

定制属性访问

类的属性由持久化引擎直接(通过字段)或者间接(通过获取方法和设置方法)访问。在xml映射文件中，用的

default-access="field|property|noop|custom.Class"属性给类控制默认的访问策略。
也可以用access属性在hibernate xml映射中控制属性级上的访问策略,如：

field是字段访问，property是属性访问. 另一个可能有用的策略是noop,它映射java持久化类中不存在的属性，这听起来
有点奇怪，但是它让你在HQL查询中指向这个"虚拟"属性(换句话说，只在HQL查询中使用数据库列).

在属性上使用访问策略noop的实例.

pom.xml:

]<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>
<groupId>hibernateTest</groupId>
<artifactId>hibernateTest</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hibernateTest</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>3.3.1.GA</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.5.2</version>
</dependency>
<dependency>
<groupId>javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.4.GA</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-proxool</artifactId>
<version>3.3.1.GA</version>
</dependency>
<dependency>
<groupId>com.oracle</groupId>
<artifactId>ojdbc14</artifactId>
<version>10.2.0.3.0</version>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<finalName>hibernateTest</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
</resource>
<resource>
<directory>src/main/java</directory>
<excludes>
<exclude>**/*.java</exclude>
</excludes>
</resource>
</resources>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>

resources/proxool.xml:

]<?xml version="1.0" encoding="UTF-8"?>
<something-else-entirely>
<proxool>
<!-- 连接池的别名  -->
<alias>proxool</alias>
<!-- proxool只能管理由自己产生的连接  -->
<driver-url>jdbc:oracle:thin:@localhost:1521:XE</driver-url>
<!--JDBC驱动程序-->
<driver-class>oracle.jdbc.driver.OracleDriver</driver-class>
<!-- 用户名与密码 -->
<driver-properties>
<property name="user" value="system" />
<property name="password" value="password" />
</driver-properties>
<!-- 允许最大连接数 ,默认是15,这里设置为20-->
<maximum-connection-count>20</maximum-connection-count>
<!-- 最小连接数 ,默认是5,其实可以不用声明它-->
<minimum-connection-count>5</minimum-connection-count>
<!-- 测试连接的sql语句 -->
<house-keeping-test-sql>select sysdate from dual</house-keeping-test-sql>
</proxool>
</something-else-entirely>

resources/hibernate.cfg.xml:

]<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration
PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory name="sessionFactory">
<property name="hibernate.connection.provider_class">
org.hibernate.connection.ProxoolConnectionProvider
</property>
<property name="hibernate.proxool.pool_alias">proxool</property>
<property name="hibernate.proxool.xml">proxool.xml</property>
<!-- 输出sql -->
<property name="hibernate.show_sql">true</property>
<!-- 格式化sql -->
<property name="hibernate.format_sql">true</property>
<!--指定数据库适配器 -->
<property name="dialect"> org.hibernate.dialect.OracleDialect </property>
<!-- 映射文件 -->
<mapping resource="hibernateTest/Student.hbm.xml" />
</session-factory>
</hibernate-configuration>

HibernateTest/Student.java , 注意：这里已经没有了age属性

]package hibernateTest;
/**
* 这里我们去掉了age属性
* @author FUHAIDONG
*/
public class Student {
private int id;
private String name;
private String address;
public int getId() {
return id;
}
@SuppressWarnings("unused")
private void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}

HibernateTest/Student.hbm.xml, 注意：这里我们添加了一个myAge映射，myAge是一个不存在的属性.

]<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping default-access="field">
<class name="hibernateTest.Student" table="STUDENT" mutable="false">
<id name="id" column="ID" type="int">
<generator class="sequence">
<!-- seq_student就是表student的主键自增的sequence -->
<param name="sequence">seq_student</param>
</generator>
</id>
<property name="name" column="name" type="string"/>
<property name="address" column="address" type="string"/>
<!-- 这里我们将AGE列映射到一个不存在的myAge属性上，使用的是access="noop" -->
<property name="myAge" column="age" type="int" access="noop"/>
</class>
</hibernate-mapping>

util/HibernateUtil.java:

]package util;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static SessionFactory sessionFactory;
static{
try {
sessionFactory = new Configuration().configure().buildSessionFactory();
} catch (Throwable e) {
throw new ExceptionInInitializerError(e);
}
}
public static SessionFactory getSessionFactory(){
return sessionFactory;
}
public static void shutdown(){
getSessionFactory().close();
}
}

util/StudentManager.java , 注意HQL语句，其中用了myAge:

]package util;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
public class StudentManager {
@SuppressWarnings("rawtypes")
public static void main(String[] args) {
Session session = HibernateUtil.getSessionFactory().openSession();
Transaction transaction1 = session.beginTransaction();
//我们在hql中使用到了Student实体中不存在的myAge属性，它是虚拟的
String hql = "select myAge from Student";
Query q = session.createQuery(hql);
List list = q.list();
for(int i=0;i<list.size();i++){
System.out.println("age: " + list.get(i));
}
transaction1.commit();
session.close();

}
}