Entity 特性支持的数据库使用示例 D 语言的 ORM 框架

程序名称：Entity 特性支持的数据库使用示例

Entity 特性支持的数据库使用示例 介绍

Entity 是 D 语言( DLang )数据库操作 ORM 框架，设计参照 javax JPA 实现，具有很好的扩展性和规范性，数据库驱动依赖
HuntLabs 开发的 database for dlang
。

特性

1. 实现了完整的 CriteriaQuery 支持

2. 对 Repository 也有部分封装

3. 完全对象化查询，不用考虑底层数据库驱动

4. 实现 EQL （Entity Query Language）实现对象化 SQL 查询语言

支持的数据库

• PostgreSQL 9.0+

• MySQL 5.1+

使用示例

import hunt.entity;

@Table("users")
class User : Entity
{
    @PrimaryKey
    @AutoIncrement
    int id;

    string name;
    double money;
    string email;
    bool status;
}

void main()
{
    DatabaseOption options = new DatabaseOption("mysql://root:123456@localhost:3306/huntblog?charset=utf-8");
    EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("default", options);
    EntityManager em = entityManagerFactory.createEntityManager();

    // begin transaction
    em.getTransaction().begin();

    // define your database existing row id in here
    int id = 10;

    auto user = em.find!User(id);
    log("User name is: ", user.name);

    // commit transaction
    em.getTransaction().commit();

    em.close();
    entityManagerFactory.close();
}

Insert row

    auto user = new User();
    user.name = "Brian";
    user.email = "[email protected]";
    user.money = 99.9;

    // insert user
    em.persist(user);
    log("User id is: ", user.id);

Delete row

    int n = em.remove!User(id);
    log("The number of users deleted is: ", n);

Update row

    auto user = em.find!User(id);
    log("User name is: ", user.name);
    user.name = "zoujiaqing";
    em.merge!User(user);
    log("The number of users updated is: ", n);

Use CriteriaQuery to find

    // create CriteriaBuilder object from em
    CriteriaBuilder builder = em.getCriteriaBuilder();

    CriteriaQuery!User criteriaQuery = builder.createQuery!User;
    Root!User root = criteriaQuery.from();
    Predicate p1 = builder.equal(root.User.id, id);
    TypedQuery!User typedQuery = em.createQuery(criteriaQuery.select(root).where(p1));

    auto user = typedQuery.getSingleResult();

    log("User name is: ", user.name);

Use CriteriaQuery to Multi-condition find

    // create CriteriaBuilder object from em
    CriteriaBuilder builder = em.getCriteriaBuilder();

    CriteriaQuery!User criteriaQuery = builder.createQuery!User;
    Root!User root = criteriaQuery.from();

    Predicate p1 = builder.lt(root.User.id, 1000);  // User id is less than 1000.
    Predicate p2 = builder.gt(root.User.money, 0);  // User money is greater than 0.
    Predicate p3 = builder.like(root.User.name, "z%");  // User name prefix is z.

    TypedQuery!User typedQuery = em.createQuery(criteriaQuery.select(root).where(builder.and(p1, p2), p3));
    User[] users = typedQuery.getResultList();

    log("The number of users found is: ", users.length);

EQL 使用

// Example for sample SELECT
auto query = em.createQuery!(User)("SELECT u FROM User u");

foreach(user; query.getResultList())
{
    logDebug(user.name);
}

Entity 特性支持的数据库使用示例 官网

https://www.huntlabs.net