Java中ResultMap的復(fù)雜映射實(shí)現(xiàn)方法

小樊
90
2024-08-11 02:46:38
欄目: 編程語言

在Java中，可以使用ResultMap來實(shí)現(xiàn)復(fù)雜的映射關(guān)系。以下是一個(gè)示例代碼，演示如何實(shí)現(xiàn)復(fù)雜的映射關(guān)系：

@Results({
    @Result(property = "id", column = "id"),
    @Result(property = "name", column = "name"),
    @Result(property = "age", column = "age"),
    @Result(property = "address", column = "address"),
    @Result(property = "department.id", column = "department_id"),
    @Result(property = "department.name", column = "department_name")
})
@Select("SELECT e.id, e.name, e.age, e.address, d.id as department_id, d.name as department_name " +
        "FROM employee e " +
        "JOIN department d ON e.department_id = d.id")
List<Employee> getEmployeesWithDepartments();

在上面的示例中，我們使用@Results注解來指定每個(gè)屬性和對(duì)應(yīng)的數(shù)據(jù)庫(kù)列之間的映射關(guān)系。其中，department.id和department.name表示Employee對(duì)象中的department屬性下的id和name屬性。

然后，在@Select注解中編寫SQL查詢語句，通過JOIN操作將employee表和department表關(guān)聯(lián)起來，并查詢出需要的字段。最終，通過getEmployeesWithDepartments方法獲取查詢結(jié)果，返回包含Employee對(duì)象的列表。

通過上述示例，可以看到Java中使用ResultMap可以很方便地實(shí)現(xiàn)復(fù)雜的映射關(guān)系。

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