如何避免在 Java 中具有相同方法体但返回类型不同的重复代码？

Question

理念：

当我使用 hibernate 时，我看到每次我必须编写某种代码。因此，我将它们移至另一种方法作为包装器。哪里会有功能接口作为参数，以便我可以在这些上下文方法中附加一些代码。

问题：

这是我的两种方法。一个返回 Object，而另一个返回 List。我怎样才能将这两种方法准确地泛化并合二为一，这样我就可以避免代码重复。

public Object objectReturnContext(Function<Session, Object> function) {
    Object object = null;
    Transaction transaction = null;

    try {
        Session session = HibernateUtil.sessionFactory().getCurrentSession();
        transaction = session.beginTransaction();
        object = function.apply(session);
        transaction.commit();
    } catch (NoResultException exception) {
        if (transaction != null) transaction.rollback();
        return object;
    } catch (HibernateException exception) {
        if (transaction != null) transaction.rollback();
        exception.getStackTrace();
    }

    return object;
}


public List<T> listReturnContext(Function<Session, List<T>> function) {
    List<T> object = null;
    Transaction transaction = null;

    try {
        Session session = HibernateUtil.sessionFactory().getCurrentSession();
        transaction = session.beginTransaction();
        object = function.apply(session);
        transaction.commit();
    } catch (NoResultException exception) {
        if (transaction != null) transaction.rollback();
        return object;
    } catch (HibernateException exception) {
        if (transaction != null) transaction.rollback();
        exception.getStackTrace();
    }

    return object;
}

为了更好地理解，这是我的整个班级。如果有人可以建议我任何更好的方法，我将非常感激。最近几天我一直在研究这个。

package com.go_task.database;


import javax.persistence.Table;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import javax.persistence.NoResultException;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Consumer;
import java.util.function.Function;


public abstract class QueryExecutionContext <T> {

    public Class<T> entity;
    public String tableName;

    public QueryExecutionContext(Class<T> entity) {
        this.entity = entity;
        this.tableName = entity.getAnnotation(Table.class).name();
    }

    public List<T> criteriaContext(CriteriaContextRunner<Session, Root<T>,
            CriteriaQuery<T>, CriteriaBuilder, List<T>> runner) {
        List<T> data = new ArrayList<>();
        Transaction transaction = null;
        try {
            Session session = HibernateUtil.sessionFactory().getCurrentSession();
            transaction = session.beginTransaction();
            CriteriaBuilder criteriaBuilder = session.getCriteriaBuilder();
            CriteriaQuery<T> criteriaQuery =
                    criteriaBuilder.createQuery(entity);
            Root<T> root = criteriaQuery.from(entity);
            data = runner.apply(session, root, criteriaQuery, criteriaBuilder);
            transaction.commit();
        } catch (HibernateException exception) {
            if (transaction != null) transaction.rollback();
            exception.getStackTrace();
        }

        return data;
    }

    public Object singleCriteriaContext(CriteriaContextRunner<Session, Root<T>,
            CriteriaQuery<T>, CriteriaBuilder, Object> runner) {
        Object data = null;
        Transaction transaction = null;
        try {
            Session session = HibernateUtil.sessionFactory().getCurrentSession();
            transaction = session.beginTransaction();
            CriteriaBuilder criteriaBuilder = session.getCriteriaBuilder();
            CriteriaQuery<T> criteriaQuery =
                    criteriaBuilder.createQuery(entity);
            Root<T> root = criteriaQuery.from(entity);
            data = runner.apply(session, root, criteriaQuery, criteriaBuilder);
            transaction.commit();
        } catch (HibernateException exception) {
            if (transaction != null) transaction.rollback();
            exception.getStackTrace();
        }

        return data;
    }

    public Object objectReturnContext(Function<Session, Object> function) {
        Object object = null;
        Transaction transaction = null;
    
        try {
            Session session = HibernateUtil.sessionFactory().getCurrentSession();
            transaction = session.beginTransaction();
            object = function.apply(session);
            transaction.commit();
        } catch (NoResultException exception) {
            if (transaction != null) transaction.rollback();
            return object;
        } catch (HibernateException exception) {
            if (transaction != null) transaction.rollback();
            exception.getStackTrace();
        }
    
        return object;
    }
    
    public List<T> listReturnContext(Function<Session, List<T>> function) {
        List<T> object = null;
        Transaction transaction = null;
    
        try {
            Session session = HibernateUtil.sessionFactory().getCurrentSession();
            transaction = session.beginTransaction();
            object = function.apply(session);
            transaction.commit();
        } catch (NoResultException exception) {
            if (transaction != null) transaction.rollback();
            return object;
        } catch (HibernateException exception) {
            if (transaction != null) transaction.rollback();
            exception.getStackTrace();
        }
    
        return object;
    }

    public void noReturnContext(Consumer<Session> consumer) {
        Transaction transaction = null;

        try {
            Session session = HibernateUtil.sessionFactory().getCurrentSession();
            transaction = session.beginTransaction();
            consumer.accept(session);
            transaction.commit();
        } catch (HibernateException exception) {
            if (transaction != null) transaction.rollback();
            exception.getStackTrace();
        }
    }
}

我稍后在我的 BaseDaoImpl.java 中扩展了 QueryExecutionContext。所以我需要知道两件事。

1. 我的方法是否正常。我使用纯休眠，没有别的。这里没有弹簧靴。
2. 如果是这样，请告诉我如何解决 objectReturnContext() 和 listReturnContext() 方法中的代码重复问题。

Answer 1

Object/List<T> 参数可以是泛型参数U：

public <U> U returnContext(Function<Session, U> function) {
    U object = null;
    Transaction transaction = null;

    try {
        Session session = HibernateUtil.sessionFactory().getCurrentSession();
        transaction = session.beginTransaction();
        object = function.apply(session);
        transaction.commit();
    } catch (NoResultException exception) {
        if (transaction != null) transaction.rollback();
        return object;
    } catch (HibernateException exception) {
        if (transaction != null) transaction.rollback();
        exception.getStackTrace();
    }

    return object;
}

U 将根据您传递给方法的function 进行推断。如果你这样称呼它：

Object o = returnContext(s -> {
    ...
    return new Object(); // just an example
});

那么U 就是Object。

如果你这样称呼它：

List<T> list = returnContext(s -> {
    ...
    return new ArrayList<T>(); // just an example
});

那么U 就是ArrayList<T>。