## 自动fetch ```java /** * 演示自动fetch,类似orm，但不同于orm，CRUD在ORM概念下过于复杂， * BeetlSQL的fetch没有那么多复杂概念，仅仅是加载对象后看看还有没有需要再加载的对象 * * * @author xiandafu */ public class S5Fetch { SQLManager sqlManager; public S5Fetch(SQLManager sqlManager) { this.sqlManager = sqlManager; } public static void main(String[] args) throws Exception { //为了简单起见，俩个sqlManager都来自同一个数据源，实际是不同数据库，甚至是NOSQL SQLManager sqlManager = SampleHelper.init(); S5Fetch fetch = new S5Fetch(sqlManager); fetch.fetchOne(); fetch.fetchMany(); } /** * */ public void fetchOne(){ UserData user = sqlManager.unique(UserData.class,1); System.out.println(user.getDept()); //fetchOne 会合并查询提高性能 List<UserData> users = sqlManager.all(UserData.class); System.out.println(users.get(0).getDept()); } public void fetchMany(){ DepartmentData dept = sqlManager.unique(DepartmentData.class,1); System.out.println(dept.getUsers()); } /** * 用户数据使用"a" sqlmanager */ @Data @Table(name="user") @Fetch public static class UserData { @Auto private Integer id; private String name; private Integer departmentId; @FetchOne("departmentId") private DepartmentData dept; } /** * 部门数据使用"b" sqlmanager */ @Data @Table(name="department") @Fetch public static class DepartmentData { @Auto private Integer id; private String name; @FetchMany("departmentId") private List<UserData> users; } } ```