Java J2EE/JPA:控制事务隔离
我希望在J2EE环境中对相同的持久性上下文使用不同的事务隔离级别。例如:Java J2EE/JPA:控制事务隔离,java,jakarta-ee,jpa,transactions,glassfish,Java,Jakarta Ee,Jpa,Transactions,Glassfish,我希望在J2EE环境中对相同的持久性上下文使用不同的事务隔离级别。例如: UserTransaction ut=...; EntityManagerFactory emf=...; EntityManager em=emf.createEntityManager; ut.begin(); em.joinTransaction(); => use RepeatableRead isolation here ... ut.commit(); ut.begin(); em.joinTrans
UserTransaction ut=...;
EntityManagerFactory emf=...;
EntityManager em=emf.createEntityManager;
ut.begin();
em.joinTransaction(); => use RepeatableRead isolation here
...
ut.commit();
ut.begin();
em.joinTransaction(); => use Serializable isolation here
...
ut.commit();
我没有办法做到这一点。当EM第一次获取DB连接时,它将从池中获取,并立即与当前XA事务一起登记。之后,再也不可能更改该DB事务的事务隔离
public class CustomDataSource extends MysqlXADataSource {
private static ThreadLocal<Integer> isolation=new ThreadLocal<Integer>(){
protected Integer initialValue() {
return Connection.TRANSACTION_REPEATABLE_READ;
};
};
public static void setTransactionIsolation(int i){
isolation.set(i);
}
private static class XAConnectionWrapper implements XAConnection {
private XAConnection delegate;
public XAConnectionWrapper(XAConnection delegate) {
this.delegate = delegate;
}
... delegate methods
@Override
public XAResource getXAResource() throws SQLException {
return new XAResourceWrapper(delegate.getXAResource());
}
@Override
public boolean equals(Object obj) {
return delegate.equals(obj);
}
@Override
public int hashCode() {
return delegate.hashCode();
}
}
private static class XAResourceWrapper implements XAResource {
private XAResource delegate;
private Field field;
... delegate methods ...
public void start(Xid xid, int flags) throws XAException {
try {
ConnectionImpl connection = (ConnectionImpl) field
.get(delegate);
connection
.setTransactionIsolation(isolation.get());
} catch (IllegalArgumentException | IllegalAccessException
| SQLException e) {
throw new RuntimeException(e);
}
delegate.start(xid, flags);
}
public XAResourceWrapper(XAResource delegate) {
try {
field = MysqlXAConnection.class
.getDeclaredField("underlyingConnection");
field.setAccessible(true);
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
} catch (SecurityException e) {
throw new RuntimeException(e);
}
this.delegate = delegate;
}
@Override
public boolean equals(Object obj) {
return delegate.equals(obj);
}
@Override
public int hashCode() {
return delegate.hashCode();
}
}
@Override
public XAConnection getXAConnection() throws SQLException {
XAConnection conn = super.getXAConnection();
return new XAConnectionWrapper(conn);
}
@Override
public XAConnection getXAConnection(String u, String p) throws SQLException {
return new XAConnectionWrapper(super.getXAConnection(u, p));
}
}
有什么想法吗?我正在使用Glassfish/EclipseLink/MySQL。我找到的解决方案是定制MySQL数据源,以返回围绕XAResource的包装器,该包装器在启动XA事务之前设置事务隔离。这样,可以在启动事务之前设置所需的事务隔离
public class CustomDataSource extends MysqlXADataSource {
private static ThreadLocal<Integer> isolation=new ThreadLocal<Integer>(){
protected Integer initialValue() {
return Connection.TRANSACTION_REPEATABLE_READ;
};
};
public static void setTransactionIsolation(int i){
isolation.set(i);
}
private static class XAConnectionWrapper implements XAConnection {
private XAConnection delegate;
public XAConnectionWrapper(XAConnection delegate) {
this.delegate = delegate;
}
... delegate methods
@Override
public XAResource getXAResource() throws SQLException {
return new XAResourceWrapper(delegate.getXAResource());
}
@Override
public boolean equals(Object obj) {
return delegate.equals(obj);
}
@Override
public int hashCode() {
return delegate.hashCode();
}
}
private static class XAResourceWrapper implements XAResource {
private XAResource delegate;
private Field field;
... delegate methods ...
public void start(Xid xid, int flags) throws XAException {
try {
ConnectionImpl connection = (ConnectionImpl) field
.get(delegate);
connection
.setTransactionIsolation(isolation.get());
} catch (IllegalArgumentException | IllegalAccessException
| SQLException e) {
throw new RuntimeException(e);
}
delegate.start(xid, flags);
}
public XAResourceWrapper(XAResource delegate) {
try {
field = MysqlXAConnection.class
.getDeclaredField("underlyingConnection");
field.setAccessible(true);
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
} catch (SecurityException e) {
throw new RuntimeException(e);
}
this.delegate = delegate;
}
@Override
public boolean equals(Object obj) {
return delegate.equals(obj);
}
@Override
public int hashCode() {
return delegate.hashCode();
}
}
@Override
public XAConnection getXAConnection() throws SQLException {
XAConnection conn = super.getXAConnection();
return new XAConnectionWrapper(conn);
}
@Override
public XAConnection getXAConnection(String u, String p) throws SQLException {
return new XAConnectionWrapper(super.getXAConnection(u, p));
}
}
public类CustomDataSource扩展了MysqlXADataSource{
私有静态ThreadLocal隔离=新ThreadLocal(){
受保护的整数初始值(){
返回Connection.TRANSACTION\u REPEATABLE\u READ;
};
};
公共静态无效设置TransactionIsolation(int i){
隔离集(i);
}
私有静态类XAConnectionWrapper实现XAConnection{
私人连接代表;
公共XAConnectionWrapper(XAConnection委托){
this.delegate=委托;
}
…委托方法
@凌驾
public XAResource getXAResource()引发SQLException{
返回新的XAResourceWrapper(delegate.getXAResource());
}
@凌驾
公共布尔等于(对象obj){
返回delegate.equals(obj);
}
@凌驾
公共int hashCode(){
返回delegate.hashCode();
}
}
私有静态类XAResourceWrapper实现XAResource{
私人资源代表;
私人领域;
…委托方法。。。
公共void start(Xid-Xid,int标志)引发异常{
试一试{
ConnectionImpl连接=(ConnectionImpl)字段
.获得(代表);
连接
.setTransactionIsolation(隔离.get());
}捕获(IllegalArgumentException | IllegalAccessException
|SQLE(异常){
抛出新的运行时异常(e);
}
委托开始(xid,标志);
}
公共XAResourceWrapper(XAResource委托){
试一试{
field=MysqlXAConnection.class
.getDeclaredField(“基础连接”);
字段。setAccessible(true);
}捕获(无此字段例外){
抛出新的运行时异常(e);
}捕获(安全异常e){
抛出新的运行时异常(e);
}
this.delegate=委托;
}
@凌驾
公共布尔等于(对象obj){
返回delegate.equals(obj);
}
@凌驾
公共int hashCode(){
返回delegate.hashCode();
}
}
@凌驾
公共XAConnection getXAConnection()引发SQLException{
XAConnection conn=super.getXAConnection();
返回新的XAConnectionWrapper(conn);
}
@凌驾
公共XAConnection getXAConnection(字符串u、字符串p)引发SQLException{
返回新的XAConnectionWrapper(super.getXAConnection(u,p));
}
}
这里有一些有趣的信息给你:@Pat B:谢谢你的链接。该博客讨论了Hibernate/Spring解决方案。据我所见,它不能在JTA环境(如J2EE)中使用,因为事务是由数据源实现启动的,而不是由JPA提供者本身启动的。