我目前正在評估JPA/Eclipselink作爲我們目前非常醜陋的jdbc數據庫訪問的替代方案。情況如下:JPA/Eclipselink @Cache失效忽略
多個客戶端訪問相同的數據庫,有時編輯相同的數據。這些數據應該定期刷新,並且只能在短時間內緩存。從我的理解來看,@Cache註釋應該完全是這樣。雖然線程休眠我在數據庫中改變一個值
...
[EL Finest]: query: 2013-06-19 14:30:55.897--UnitOfWork(31211079)--Thread(Thread[main,5,main])--Execute query ReadAllQuery(referenceClass=Todo sql="SELECT ID, DESCRIPTION, SUMMARY FROM TODO")
[EL Finest]: connection: 2013-06-19 14:30:55.907--ServerSession(7427424)--Connection(7633596)--Thread(Thread[main,5,main])--Connection acquired from connection pool [default].
[EL Fine]: sql: 2013-06-19 14:30:55.907--ServerSession(7427424)--Connection(7633596)--Thread(Thread[main,5,main])--SELECT ID, DESCRIPTION, SUMMARY FROM TODO
[EL Finest]: connection: 2013-06-19 14:30:55.924--ServerSession(7427424)--Connection(7633596)--Thread(Thread[main,5,main])--Connection released to connection pool [default].
Query 1 read
1: Todo [id=1, summary=s1, description=d1]
1: Todo [id=2, summary=qwet, description=d2]
[EL Finest]: query: 2013-06-19 14:31:25.932--UnitOfWork(31211079)--Thread(Thread[main,5,main])--Execute query ReadAllQuery(referenceClass=Todo sql="SELECT ID, DESCRIPTION, SUMMARY FROM TODO")
[EL Finest]: connection: 2013-06-19 14:31:25.932--ServerSession(7427424)--Connection(7633596)--Thread(Thread[main,5,main])--Connection acquired from connection pool [default].
[EL Fine]: sql: 2013-06-19 14:31:25.932--ServerSession(7427424)--Connection(7633596)--Thread(Thread[main,5,main])--SELECT ID, DESCRIPTION, SUMMARY FROM TODO
[EL Finest]: connection: 2013-06-19 14:31:25.934--ServerSession(7427424)--Connection(7633596)--Thread(Thread[main,5,main])--Connection released to connection pool [default].
Query 2 read
1: Todo [id=1, summary=s1, description=d1]
2: Todo [id=1, summary=s1, description=d1]
true
1: Todo [id=2, summary=qwet, description=d2]
2: Todo [id=2, summary=qwet, description=d2]
true
:
下面的代碼是基於JPA /的EclipseLink上Vogella
@Entity
@Cache(expiry = 100)
public class Todo {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String summary;
private String description;
... getter/setter/toString omited
}
public static void main(String[] args) throws InterruptedException {
EntityManagerFactory factory =
Persistence.createEntityManagerFactory("mysql");
EntityManager em = factory.createEntityManager();
TypedQuery<Todo> q = em.createQuery("SELECT t FROM Todo t", Todo.class);
List<Todo> todoList = q.getResultList();
System.out.println("Query 1 read");
for (int i = 0; i < todoList.size(); i++) {
System.out.println("1: " + todoList.get(i));
}
Thread.sleep(30000);
TypedQuery<Todo> q2 =
em.createQuery("SELECT t FROM Todo t", Todo.class);
// q2.setHint("javax.persistence.cache.storeMode", "REFRESH");
List<Todo> todoList2 = q2.getResultList();
System.out.println("Query 2 read");
for (int i = 0; i < todoList.size(); i++) {
System.out.println("1: " + todoList.get(i));
System.out.println("2: " + todoList2.get(i));
System.out.println(todoList.get(i) == todoList2.get(i));
}
}
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="mysql" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<properties>
<property name="javax.persistence.jdbc.password" value="" />
<property name="javax.persistence.jdbc.user" value="root" />
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/test" />
<property name="javax.persistence.ddl-generation" value="create-tables" />
<property name="javax.persistence.logging.level" value="ALL" />
<property name="eclipselink.logging.level" value="ALL"/>
</properties>
</persistence-unit>
</persistence>
運行PROGRAMM產生以下輸出。我期望從數據庫中獲得新值,因爲緩存中的值應該已過期。它似乎代碼簡單地忽略@Cache註釋。我也嘗試過其他各種設置,例如type = CacheType.NONE和alwaysRefresh = true,但沒有任何改變。
當我添加storeMode-QueryHint時,查詢總是刷新結果。這不完全是我想要的,似乎我需要將它添加到每個非常容易出錯的查詢中。但是,Cache註釋被忽略仍然很奇怪。
我也嘗試使用DescriptorCustomizer,但它也沒有效果,儘管正在使用(用斷點測試)。
public void customize(ClassDescriptor descriptor) {
descriptor.alwaysRefreshCache();
descriptor.alwaysRefreshCacheOnRemote();
descriptor.disableCacheHits();
descriptor.disableCacheHitsOnRemote();
}
更新:
有些話我開發的系統。它是讀取/寫入我們的主數據的模塊。因此,例如,在同一用戶的內存中存在兩次用戶對象時,感覺不對。另外,在我測試了@ReadOnly註解之後,我注意到@Cache註釋的isolation參數似乎可行,但仍然沒有任何關於expire,alwaysrefresh等的信息。
您正在使用相同的EntityManager實例。緩存設置適用於共享緩存,而EntityManager需要將相同的對象保留在內存中,直到它被關閉或清除 - 否則簡單的查找操作可能會清除正在運行的事務中的更改。獲得一個新的EntityManager或在Thread.sleep調用之前清除現有的一個 – Chris
但我希望刷新現有的對象。另外,當我在第一個數據庫讀取後分離對象或清除時,我得到新的對象。在同一時間在應用程序中擁有兩個不同狀態的相同數據庫行並不是一個非常令人不爽的想法。 主要是我希望它每次都刷新(或者超時後更好)我訪問數據庫。 – ssindelar