将应用程序迁移到使用guice-如何将事务注入现有对象?

我对Guice是个新手,我正在将它应用到一个具有大量遗留代码的应用程序中。它有几个类如下所示:

public final class DataAccessClass {

    private Transaction txn;

    @Inject //This was just added
    public DataAccessClass(/* injectable parameters */, Transaction txn) {

        this.txn = txn;
    }

    //Maybe add @Inject here to set a new transaction when it changes?
    public void setTransaction(Transaction txn) {

        this.txn = txn;
    }

    public void writeData(/* parameters for data to be written */) {

        //Write data using the current instance of 'txn'
    }
}

很明显,如何使用guice来绑定从不更改的实例,但是那些更改的实例(即事务)呢?有没有一种方法可以让我在事务更改时使用guice来注入不同的事务实例? 请注意,事务实例不是受良好支持的JPA/Hibernate/Spring事务之一。

我能想到的最不具入侵性的方法(避免一次性迁移每个使用事务的类)将仅在实例化对象时使用guice注入事务,并保留现有的应用程序代码,在必要时更新事务。例如,此提供程序可用于向当前事务实例注入新对象:

public final class TransactionProvider implements Provider<Transaction> {

    /** Nullable transaction that should be used for all operations at the moment */
    private Transaction txn;

    public TransactionProvider(Transaction txn) {

        this.txn = txn;
    }

    /**
     * @param txn Nullable transaction to use for all operations at the moment
     */
    public void setTransaction(Transaction txn) {

        this.txn = txn;
    }

    /* Provider methods */

    public Transaction get() {

        return this.txn;
    }
}

应用程序逻辑如下所示:

public final class Application {

    private final Provider<Transaction> transactionProvider;
    private final DataAccessClass dao; //Instance provided by Guice

    public void scopedOperation() {

        //Use a fresh transaction for this operation
        final Transaction txn = ...;

        //Make transaction available to Guice (for new objects) and to legacy (already-instantiated) DAO classes
        this.transactionProvider.setTransaction(txn);
        this.dao.setTransaction(txn); //Legacy approach - can this be updated?

        //Do some kind of data operation under the scope of the current transaction
        try {
            this.dao.writeData(...);
        } catch (Exception e) {
            txn.abort();
            throw new RuntimeException("Operation failed", e);
        }

        //The operation is over now
        this.txn.commit();
    }

是否有其他方法更新现有类使用的事务实例,而不必一次迁移每个类?