Java的ORM框架有很多，但由于Java語言的限制大部分都不夠優(yōu)雅也不夠簡(jiǎn)單，所以作者只能另辟蹊徑造輪子了。照舊先看示例代碼了解個(gè)大概，然后再解釋實(shí)現(xiàn)原理。

public CompletableFuture<Void> insert() { var obj = new sys.entities.Demo('MyName'); //構(gòu)造參數(shù)為主鍵 obj.Age = 100; //設(shè)置實(shí)體屬性的值 return obj.saveAsync();}2. Update

更新單個(gè)實(shí)體（必須具備主鍵）

public CompletableFuture<Void> update(sys.entities.Demo obj) { obj.Age = 200; return obj.saveAsync();}

根據(jù)條件更新（必須指定條件以防誤操作）

public CompletableFuture<?> update() { var cmd = new SqlUpdateCommand<sys.entities.Demo>(); cmd.update(e -> e.City = 'Wuxi'); //更新字段 cmd.update(e -> e.Age = e.Age + 1); //更新累加字段 cmd.where(e -> e.Name == 'Johne'); //更新的條件 var outs = cmd.output(e -> e.Age); //更新的同時(shí)返回指定字段 return cmd.execAsync().thenApply(rows -> { System.out.println('更新記錄數(shù): ' + rows); System.out.println('返回的值: ' + outs.get(0)); return 'Done.'; });}3. Delete

刪除單個(gè)實(shí)體（必須具備主鍵）

public CompletableFuture<Void> update(sys.entities.Demo obj) { obj.markDeleted(); //先標(biāo)記為刪除狀態(tài) return obj.saveAsync(); //再調(diào)用保存方法}

根據(jù)條件刪除（必須指定條件以防誤操作）

public CompletableFuture<?> delete() { var cmd = new SqlDeleteCommand<sys.entities.Demo>(); cmd.where(e -> e.Age < 0 || e.Age > 200); return cmd.execAsync();}4. Transaction

  由于作者討厭隱式事務(wù)，所以事務(wù)命令必須顯式指定。

public CompletableFuture<?> transaction() { var obj1 = new sys.entities.Demo('Demo1'); obj1.Age = 11; var obj2 = new sys.entities.Demo('Demo2'); obj2.Age = 22; return DataStore.DemoDB.beginTransaction().thenCompose(txn -> { //開始事務(wù) return obj1.saveAsync(txn) //事務(wù)保存obj1 .thenCompose(r -> obj2.saveAsync(txn)) //事務(wù)保存obj2 .thenCompose(r -> txn.commitAsync()); //遞交事務(wù) }).thenApply(r -> 'Done');}5. Sql查詢

Where條件

public CompletableFuture<?> query(String key) { var q = new SqlQuery<sys.entities.Demo>(); q.where(e -> e.Age > 10 && e.Age < 80); if (key != null) q.andWhere(e -> e.Name.contains(key)); //拼接條件 return q.toListAsync(); //返回List<sys.entities.Demo>}

分頁查詢

public CompletableFuture<?> query(int pageSize, int pageIndex) { var q = new SqlQuery<sys.entities.Demo>(); return q.skip(pageSize * pageIndex) .take(pageSize) .toListAsync();}

結(jié)果映射至匿名類

public CompletableFuture<?> query() { var q = new SqlQuery<sys.entities.Demo>(); return q.toListAsync(e -> new Object() { //返回List<匿名類> public final String Name = e.Name; //匿名類屬性 = 實(shí)體屬性表達(dá)式 public final int Age = e.Age + 10; public final String Father = e.Parent.Name; }).thenApply(appbox.data.JsonResult::new);}

結(jié)果映射至繼承的匿名類

public CompletableFuture<?> query() { var q = new SqlQuery<sys.entities.Demo>(); q.where(e -> e.Parent.Name == 'Rick'); return q.toListAsync(e -> new sys.entities.Demo() { //返回List<? extens Demo> public final String Father = e.Parent.Name; });}

結(jié)果映射至樹狀結(jié)構(gòu)列表

public CompletableFuture<?> tree() { var q = new SqlQuery<sys.entities.Demo>(); q.where(t -> t.Name == 'Rick'); return q.toTreeAsync(t -> t.Childs); //參數(shù)指向EntitySet(一對(duì)多成員）}

EntityRef(一對(duì)一引用的實(shí)體成員)自動(dòng)Join

public CompletableFuture<?> query() { var q = new SqlQuery<sys.entities.Customer>(); q.where(cus -> cus.City.Name == 'Wuxi'); return q.toListAsync();}生成的Sql:Select t.* From 'Customer' t Left Join 'City' j1 On j1.'Code'=t.'CityCode'

手工指定Join

public CompletableFuture<?> join() { var q = new SqlQuery<sys.entities.Customer>(); var j = new SqlQueryJoin<sys.entities.City>(); q.leftJoin(j, (cus, city) -> cus.CityCode == city.Code); q.where(j, (cus, city) -> city.Name == 'Wuxi'); return q.toListAsync();}

子查詢

public CompletableFuture<?> subQuery() { var sq = new SqlQuery<sys.entities.Demo>(); sq.where(s -> s.ParentName == 'Rick'); var q = new SqlQuery<sys.entities.Demo>(); q.where(t -> DbFunc.in(t.Name, sq.toSubQuery(s -> s.Name))); return q.toListAsync();}

GroupBy

public CompletableFuture<?> groupBy() { var q = new SqlQuery<sys.entities.Demo>(); q.groupBy(t -> t.ParentName) //多個(gè)可重復(fù) .having(t -> DbFunc.sum(t.Age) > 10); return q.toListAsync(t -> new Object() { public final String group = t.ParentName == null ? '可憐的孩子' : t.ParentName; public final int totals = DbFunc.sum(t.Age); }).thenApply(appbox.data.JsonResult::new);}二、實(shí)現(xiàn)原理

  其實(shí)以上的示例代碼并非最終運(yùn)行的代碼，作者利用Eclipse jdt將上述代碼在編譯發(fā)布服務(wù)模型時(shí)分析轉(zhuǎn)換為最終的運(yùn)行代碼，具體過程如下：

1. jdt分析服務(wù)虛擬代碼生成AST抽象語法樹;2. 遍歷AST樹，將實(shí)體對(duì)象的讀寫屬性改寫為getXXX(), setXXX();

var name = obj.Name; //讀實(shí)體屬性obj.Name = 'Rick'; //寫實(shí)體屬性

改寫為:

var name = obj.getName();obj.setName('Rick');

3. 遍歷AST樹，將查詢相關(guān)方法的參數(shù)轉(zhuǎn)換為運(yùn)行時(shí)表達(dá)式；

public CompletableFuture<?> query(String key) { var q = new SqlQuery<sys.entities.Employee>(); q.where(e -> e.Manager.Name + 'a' == key + 'b'); return q.toListAsync();}

轉(zhuǎn)換為:

public CompletableFuture<?> query(String key) { var q = new appbox.store.query.SqlQuery<>(-7018111290459553788L, SYS_Employee.class); q.where(e -> e.m('Manager').m('Name').plus('a').eq(key + 'b')); return q.toListAsync();}

4. 根據(jù)服務(wù)模型使用到的實(shí)體模型生成相應(yīng)實(shí)體的運(yùn)行時(shí)代碼；5. 最后編譯打包服務(wù)模型的字節(jié)碼。

以上請(qǐng)參考源碼的ServiceCodeGenerator及EntityCodeGenerator類。

  作者寫了個(gè)簡(jiǎn)單查詢的服務(wù)，測(cè)試配置為MacBook主機(jī)(wrk壓測(cè) + 數(shù)據(jù)庫)->4核I7虛擬機(jī)(服務(wù)端)，測(cè)試結(jié)果如下所示qps可達(dá)1萬，已包括實(shí)體映射轉(zhuǎn)換及序列化傳輸?shù)人虚_銷。這里順便提一下，由于框架是全異步的，所以沒有使用傳統(tǒng)的JDBC驅(qū)動(dòng)，而是使用了jasync-sql(底層為Netty)來驅(qū)動(dòng)數(shù)據(jù)庫。

wrk -c200 -t2 -d20s -s post_bin.lua http://10.211.55.8:8000/apiRunning 20s test @ http://10.211.55.8:8000/api 2 threads and 200 connections Thread Stats Avg Stdev Max +/- Stdev Latency 18.97ms 5.84ms 89.15ms 81.55% Req/Sec 5.32k 581.92 6.48k 65.00% 211812 requests in 20.02s, 36.76MB readRequests/sec: 10578.90Transfer/sec: 1.84MB

以上就是這么優(yōu)雅的Java ORM沒見過吧!的詳細(xì)內(nèi)容，更多關(guān)于java orm的資料請(qǐng)關(guān)注好吧啦網(wǎng)其它相關(guān)文章！