一、EhCache的主要特性：
- 快速 2. 简单 3. 多种缓存策略 4. 缓存数据有两级：内存和磁盘，因此无需担心容量问题
5. 缓存数据会在虚拟机重启的过程中写入磁盘 6. 可以通过RMI、可插入API等方式进行分布式缓存
7. 具有缓存和缓存管理器的侦听接口 8. 支持多缓存管理器实例，以及一个实例的多个缓存区域
9. 提供Hibernate的缓存实现
二、hibernate.cfg.xml 内容：
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- Hibernate 连接数据库的基本信息 --> <property name="connection.username">scott</property> <property name="connection.password">java</property> <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property> <property name="connection.url">jdbc:oracle:thin:@localhost:1521:orcl</property> <!-- Hibernate 的基本配置 --> <!-- Hibernate 使用的数据库方言 --> <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property> <!-- 运行时是否打印 SQL --> <property name="show_sql">true</property> <!-- 运行时是否格式化 SQL --> <property name="format_sql">true</property> <!-- 生成数据表的策略 --> <property name="hbm2ddl.auto">update</property> <!-- 设置 Hibernate 的事务隔离级别 --> <property name="connection.isolation">2</property> <!-- 删除对象后, 使其 OID 置为 null --> <property name="use_identifier_rollback">true</property> <!-- 配置 C3P0 数据源 --> <!-- <property name="hibernate.c3p0.max_size">10</property> <property name="hibernate.c3p0.min_size">5</property> <property name="c3p0.acquire_increment">2</property> <property name="c3p0.idle_test_period">2000</property> <property name="c3p0.timeout">2000</property> <property name="c3p0.max_statements">10</property> --> <!-- 设定 JDBC 的 Statement 读取数据的时候每次从数据库中取出的记录条数 --> <property name="hibernate.jdbc.fetch_size">100</property> <!-- 设定对数据库进行批量删除，批量更新和批量插入的时候的批次大小 --> <property name="jdbc.batch_size">30</property> <!-- 启用二级缓存 --> <property name="cache.use_second_level_cache">true</property> <!-- 配置使用的二级缓存的产品 --> <property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property> <!-- 配置启用查询缓存 --> <property name="cache.use_query_cache">true</property> <!-- 配置管理 Session 的方式 --> <property name="current_session_context_class">thread</property> <!-- 需要关联的 hibernate 映射文件 .hbm.xml --> <mapping resource="com/atguigu/hibernate/entities/Department.hbm.xml"/> <mapping resource="com/atguigu/hibernate/entities/Employee.hbm.xml"/> <class-cache usage="read-write" class="com.atguigu.hibernate.entities.Employee"/> <class-cache usage="read-write" class="com.atguigu.hibernate.entities.Department"/> <collection-cache usage="read-write" collection="com.atguigu.hibernate.entities.Department.emps"/> </session-factory> </hibernate-configuration>
三、ehcache.xml 内容：
<ehcache> <!-- Sets the path to the directory where cache .data files are created. If the path is a Java System Property it is replaced by its value in the running VM. The following properties are translated: user.home - User‘s home directory user.dir - User‘s current working directory java.io.tmpdir - Default temp file path --> <!-- 指定一个目录：当 EHCache 把数据写到硬盘上时, 将把数据写到这个目录下. --> <diskStore path="d:\\tempDirectory"/> <!--Default Cache configuration. These will applied to caches programmatically created through the CacheManager. The following attributes are required for defaultCache: maxInMemory - Sets the maximum number of objects that will be created in memory eternal - Sets whether elements are eternal. If eternal, timeouts are ignored and the element is never expired. timeToIdleSeconds - Sets the time to idle for an element before it expires. Is only used if the element is not eternal. Idle time is now - last accessed time timeToLiveSeconds - Sets the time to live for an element before it expires. Is only used if the element is not eternal. TTL is now - creation time overflowToDisk - Sets whether elements can overflow to disk when the in-memory cache has reached the maxInMemory limit. --> <!-- 设置缓存的默认数据过期策略 --> <defaultCache maxElementsInMemory="10000" eternal="false" timeToIdleSeconds="120" timeToLiveSeconds="120" overflowToDisk="true" /> <!-- 设定具体的命名缓存的数据过期策略。每个命名缓存代表一个缓存区域 缓存区域(region)：一个具有名称的缓存块，可以给每一个缓存块设置不同的缓存策略。 如果没有设置任何的缓存区域，则所有被缓存的对象，都将使用默认的缓存策略。即：<defaultCache.../> Hibernate 在不同的缓存区域保存不同的类/集合。 对于类而言，区域的名称是类名。如:com.atguigu.domain.Customer 对于集合而言，区域的名称是类名加属性名。如com.atguigu.domain.Customer.orders --> <!-- name: 设置缓存的名字,它的取值为类的全限定名或类的集合的名字 maxElementsInMemory: 设置基于内存的缓存中可存放的对象最大数目 eternal: 设置对象是否为永久的, true表示永不过期, 此时将忽略timeToIdleSeconds 和 timeToLiveSeconds属性; 默认值是false timeToIdleSeconds:设置对象空闲最长时间,以秒为单位, 超过这个时间,对象过期。 当对象过期时,EHCache会把它从缓存中清除。如果此值为0,表示对象可以无限期地处于空闲状态。 timeToLiveSeconds:设置对象生存最长时间,超过这个时间,对象过期。 如果此值为0,表示对象可以无限期地存在于缓存中. 该属性值必须大于或等于 timeToIdleSeconds 属性值 overflowToDisk:设置基于内存的缓存中的对象数目达到上限后,是否把溢出的对象写到基于硬盘的缓存中 --> <cache name="com.atguigu.hibernate.entities.Employee" maxElementsInMemory="1" eternal="false" timeToIdleSeconds="300" timeToLiveSeconds="600" overflowToDisk="true" /> <cache name="com.atguigu.hibernate.entities.Department" maxElementsInMemory="1000" eternal="true" timeToIdleSeconds="0" timeToLiveSeconds="0" overflowToDisk="false" /> <cache name="com.atguigu.hibernate.entities.Department.emps" maxElementsInMemory="1000" eternal="true" timeToIdleSeconds="0" timeToLiveSeconds="0" overflowToDisk="false" /> </ehcache>
四、Employee.java 和 Department.java 实体类
public class Employee {
private Integer id;
private String name;
private float salary;
private String email;
private Department dept;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getSalary() {
return salary;
}
public void setSalary(float salary) {
this.salary = salary;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Department getDept() {
return dept;
}
public void setDept(Department dept) {
this.dept = dept;
}
@Override
public String toString() {
return "Employee [id=" + id + "]";
}
public Employee(String email, float salary, Department dept) {
super();
public class Department {
private Integer id;
private String name;
private Set<Employee> emps = new HashSet<>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Employee> getEmps() {
return emps;
}
public void setEmps(Set<Employee> emps) {
this.emps = emps;
}
@Override
public String toString() {
return "Department [id=" + id + "]";
}
}
五、Employee.hbm.xml 和 Department.hbm.xml 的配置文件
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.atguigu.hibernate.entities.Employee" table="GG_EMPLOYEE"> <cache usage="read-write"/> <id name="id" type="java.lang.Integer"> <column name="ID" /> <generator class="native" /> </id> <property name="name" type="java.lang.String"> <column name="NAME" /> </property> <property name="salary" type="float"> <column name="SALARY" /> </property> <property name="email" type="java.lang.String"> <column name="EMAIL" /> </property> <many-to-one name="dept" class="com.atguigu.hibernate.entities.Department"> <column name="DEPT_ID" /> </many-to-one> </class> <query name="salaryEmps"><![CDATA[FROM Employee e WHERE e.salary > :minSal AND e.salary < :maxSal]]></query> </hibernate-mapping>
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.atguigu.hibernate.entities.Department" table="GG_DEPARTMENT"> <cache usage="read-write"/> <id name="id" type="java.lang.Integer"> <column name="ID" /> <generator class="native" /> </id> <property name="name" type="java.lang.String"> <column name="NAME" /> </property> <set name="emps" table="GG_EMPLOYEE" inverse="true" lazy="true"> <key> <column name="DEPT_ID" /> </key> <one-to-many class="com.atguigu.hibernate.entities.Employee" /> </set> </class> </hibernate-mapping>
时间： 2024-10-10 10:10:03