Data source architecture model line data entry

Note: If you don’t understand, please don’t read it. This article is not for Java, so Java lovers can just skip it.

1. Concept

Row Data Gateway: An object that serves as the entry point for a single record in the data source, with one instance per row.

2. Simple implementation of row data entry

In order to facilitate understanding, let’s simply implement it first:

<?php
/**
 * 行数据入口类
 */
class OrderGateway {
    /*定义元数据映射*/
    private $_name;
    private $_id;
 
    public function __construct($id, $name) {
        $this->setId($id);
        $this->setName($name);
    }
 
    public function getName() {
        return $this->_name;
    }
 
    public function setName($name) {
        $this->_name = $name;
    }
 
    public function getId() {
        return $this->_id;
    }
 
    public function setId($id) {
        $this->_id = $id;
    }
 
    /**
     * 入口类自身拥有更新操作
     */
    public function update() {
        $data = array(&#39;id&#39; => $this->_id, &#39;name&#39; => $this->_name);
 
        $sql = "UPDATE order SET ";
        foreach ($data as $field => $value) {
            $sql .= "`" . $field . "` = &#39;" . $value . "&#39;,";
        }
        $sql = substr($sql, 0, -1);
        $sql .= " WHERE id = " . $this->_id;
        return DB::query($sql);
    }
 
    /**
     * 入口类自身拥有插入操作
     */
    public function insert() {
        $data = array(&#39;name&#39; => $this->_name);
 
        $sql = "INSERT INTO order ";
        $sql .= "(`" . implode("`,`", array_keys($data)) . "`)";
        $sql .= " VALUES(&#39;" . implode("&#39;,&#39;", array_values($data)) . "&#39;)";
 
        return DB::query($sql);
    }
 
    public static function load($rs) {
        /* 此处可加上缓存 */
        return new OrderGateway($rs[&#39;id&#39;] ? $rs[&#39;id&#39;] : NULL, $rs[&#39;name&#39;]);
    }
 
}
 
/**
 * 为了从数据库中读取信息，设置独立的OrderFinder娄。
 */
class OrderFinder {
    public function find($id) {
        $sql = "SELECT * FROM order WHERE id = " . $id;
        $rs = DB::query($sql);
 
        return OrderGateway::load($rs);//这里返回的行对象
    }
 
    public function findAll() {
        $sql = "SELECT * FROM order";
        $rs = DB::query($sql);
 
        $result = array();
        if (is_array($rs)) {
            foreach ($rs as $row) {
                $result[] = OrderGateway::load($row);
            }
        }
 
        return $result;
    }
 
}
 
class DB {
 
    /**
     * 这只是一个执行SQL的演示方法
     * @param string $sql   需要执行的SQL
     */
    public static function query($sql) {
        echo "执行SQL: ", $sql, " <br />";
    }
}
 
/**
 * 客户端调用
 */
class Client {
    public static function main() {
        header("Content-type:text/html; charset=utf-8");
 
        /* 写入示例 */
        $data = array(&#39;name&#39; => &#39;start&#39;);
        $order = OrderGateway::load($data);
        $order->insert();
 
        /* 更新示例 */
        $data = array(&#39;id&#39; => 1, &#39;name&#39; => &#39;stop&#39;);
        $order = OrderGateway::load($data);
        $order->setName(&#39;xxxxxx&#39;);
        $order->update();
 
        /* 查询示例 */
        $finder = new OrderFinder();
        $order = $finder->find(1);
        echo $order->getName();
    }
}
 
Client::main();
?>

3. Operation mechanism

● Row data entry is an object that is very similar to a single record. In this object, each column in the database for a domain.

●Row data entry generally enables any conversion from data source type to in-memory type.

●There is no domain logic in the row data entry. If it exists, it is an active record.

●As you can see in the example, in order to read information from the database, set up an independent OrderFinder class. Of course, you can also choose not to create a new class and use a static search method, but it does not support polymorphism that requires different search methods for different data sources. Therefore it is best to set the object of the search method separately here.

●Row data entry can be used not only for tables but also for views. What needs attention is the update operation of the view.

● It is a good practice to have "Define Metadata Mapping" visible in the code so that all database access code can be automatically generated during the automatic creation process.

4. Usage Scenarios

4.1 Transaction scripts

can separate the database access code well and can be easily reused by different transaction scripts. However, you may find that business logic is repeated in multiple scripts, and this logic may be useful in row data entry. Continuously moving this logic will evolve row data entries into active records, which reduces duplication of business logic.

4.2 Domain Model

If you want to change the structure of the database but do not want to change the domain logic, using row data entry is a good choice. In most cases, data mappers are more suitable for domain models.

Row data entries can be used together with data mappers. Although this may seem a bit redundant, this approach can be effective when row data entries are automatically generated from metadata and the data mapper is implemented manually.

4.3 Table module (not considered)