核心技术靠化缘是要不来的——自己动手写ORM框架
开源市场上的Java的ORM框架一个都不好用，所以花了几天时间自己撸了一个 OrmKids，欢迎大家下载学习。遇到问题请关注公众号进群大家一起讨论。
支持分库分表的MySQL单表ORM框架，暂用于学习，后续会在生产环境进行检验
功能特性
- 代码简洁，没有任何依赖项，除了使用时需要用到MySQL driver
- 易于使用，无须复杂的配置
- 提供自动创建表功能
- 支持分库又分表，可以只分库，也可以只分表
- 支持groupby/having
- 支持原生SQL
- 支持事件回调，可用于服务跟踪调试和动态sql改写
不支持多表关联
- 多表比较复杂，实现成本高，学习成本也高，容易出错
- 常用的多表的操作一般都可以使用多条单表操作组合实现
- 在分库分表的场合，很少使用多表操作
- 不使用外键，专注于sql逻辑
db.withinTx
对于复杂的多表查询和批量数据处理，可以使用该方法。 用户可以获得原生的jdbc链接，通过编写jdbc代码来实现。
Q
用户可以使用Q对象构建复杂的SQL查询
其它数据库支持
暂时没有
实体接口
/**
* 所有的实体类必须实现该接口
*/
public interface IEntity {
/**
* 表名
* @return
*/
String table();
/**
* 分表必须覆盖此方法
* @return
*/
default String suffix() {
return null;
}
default String tableWithSuffix() {
return tableWith(suffix());
}
default String tableWith(String suffix) {
return Utils.tableWithSuffix(table(), suffix);
}
/**
* 定义表的物理结构属性如engine=innodb，用于动态创建表
* @return
*/
TableOptions options();
/**
* 定义表的主键和索引信息，用于动态创建表
* @return
*/
TableIndices indices();
}单表单主键
@Table
public class User implements IEntity {
@Column(name = "id", type = "int", autoincrement = true, nullable = false)
private Integer id;
@Column(name = "name", type = "varchar(255)", nullable = false)
private String name;
@Column(name = "nick", type = "varchar(255)", nullable = false)
private String nick;
@Column(name = "passwd", type = "varchar(255)")
private String passwd;
@Column(name = "created_at", type = "datetime", nullable = false, defaultValue = "now()")
private Date createdAt;
public User() {
}
public User(String name, String nick, String passwd) {
this.name = name;
this.nick = nick;
this.passwd = passwd;
}
public Integer getId() {
return id;
}
public String getName() {
return name;
}
public String getNick() {
return nick;
}
public String getPasswd() {
return passwd;
}
public Date getCreatedAt() {
return createdAt;
}
@Override
public TableOptions options() {
return new TableOptions().option("engine", "innodb");
}
@Override
public TableIndices indices() {
return new TableIndices().primary("id").unique("name");
}
@Override
public String table() {
return "user";
}
}单表复合主键
@Table
public class Member implements IEntity {
@Column(name = "user_id", type = "int", nullable = false)
private Integer userId;
@Column(name = "group_id", type = "int", nullable = false)
private Integer groupId;
@Column(name = "title", type = "varchar(255)")
private String title;
@Column(name = "created_at", type = "datetime", nullable = false, defaultValue = "now()")
private Date createdAt;
public Member() {
}
public Member(Integer userId, Integer groupId, String title, Date createdAt) {
this.userId = userId;
this.groupId = groupId;
this.title = title;
this.createdAt = createdAt;
}
public Integer getUserId() {
return userId;
}
public Integer getGroupId() {
return groupId;
}
public String getTitle() {
return title;
}
public Date getCreatedAt() {
return createdAt;
}
@Override
public TableOptions options() {
return new TableOptions().option("engine", "innodb");
}
@Override
public TableIndices indices() {
return new TableIndices().primary("user_id", "group_id");
}
@Override
public String table() {
return "member";
}
}分库接口
public interface IGridable<T extends IEntity> {
/**
* 根据实体对象选择分库索引
*/
int select(int dbs, T t);
/**
* 根据特定参数选择分库索引
*/
int select(int dbs, Object... params);
}分库分表
@Table
public class BookShelf implements IEntity {
public final static int PARTITIONS = 4;
@Column(name = "user_id", type = "varchar(255)", nullable = false)
private String userId;
@Column(name = "book_id", type = "varchar(255)", nullable = false)
private String bookId;
@Column(name = "comment", type = "varchar(255)")
private String comment;
@Column(name = "created_at", type = "datetime", nullable = false, defaultValue = "now()")
private Date createdAt;
public BookShelf() {
}
public BookShelf(String userId, String bookId, String comment, Date createdAt) {
this.userId = userId;
this.bookId = bookId;
this.comment = comment;
this.createdAt = createdAt;
}
public String getUserId() {
return userId;
}
public String getBookId() {
return bookId;
}
public void setComment(String comment) {
this.comment = comment;
}
public String getComment() {
return comment;
}
public Date getCreatedAt() {
return createdAt;
}
@Override
public String table() {
return "book_shelf";
}
@Override
public TableOptions options() {
return new TableOptions().option("engine", "innodb");
}
@Override
public TableIndices indices() {
return new TableIndices().primary("user_id", "book_id");
}
/*
* 分表策略
*/
@Override
public String suffix() {
var crc32 = new CRC32();
crc32.update(userId.getBytes(Utils.UTF8));
return String.valueOf(Math.abs(crc32.getValue()) % PARTITIONS);
}
/**
* 分库策略
*/
public static class GridStrategy<D extends DB> implements IGridable<BookShelf> {
@Override
public int select(int dbs, BookShelf t) {
return Math.abs(t.getUserId().hashCode()) % dbs;
}
@Override
public int select(int dbs, Object... params) {
String userId = (String) params[0];
return Math.abs(userId.hashCode()) % dbs;
}
}
}定义单个数据库
public class DemoDB extends DB {
private DataSource ds;
public DemoDB(String name, String uri) {
this(name, new HashMap<>(), uri);
}
public DemoDB(String name, Map<Class<? extends IEntity>, Meta> metas, String uri) {
super(name, metas);
var ds = new MysqlConnectionPoolDataSource(); // 连接池
ds.setUrl(uri);
this.ds = ds;
}
@Override
protected Connection conn() { // 获取链接
try {
return ds.getConnection();
} catch (SQLException e) {
throw new KidsException(e);
}
}
}定义网格数据库——分库
public class GridDemoDB extends GridDB<DemoDB> {
/**
* 传进来多个DB对象
*/
public GridDemoDB(DemoDB[] dbs) {
super(dbs);
this.registerGridables();
}
/*
* 注册实体类的分库策略
*/
@Override
public void registerGridables() {
this.gridWith(BookShelf.class, new BookShelf.GridStrategy<DemoDB>());
}
}单表单主键增删改查
public class DemoSimplePk {
private final static String URI = "jdbc:mysql://localhost:3306/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8";
public static void main(String[] args) {
var db = new DemoDB("demo", URI);
try {
db.create(User.class); // 创建表
var user = new User("test1", "nick1", "passwd1");
db.insert(user); // 插入
System.out.println(user.getId());
user = db.get(User.class, user.getId()); // 主键查询
System.out.printf("%s %s %s %s %s\n", user.getId(), user.getName(), user.getNick(), user.getPasswd(),
user.getCreatedAt());
user = new User("test2", "nick2", "passwd2");
db.insert(user); // 再插入
var count = db.count(User.class); // 查询总行数
System.out.println(count);
var users = db.find(User.class); // 列出所有行
System.out.println(users.size());
for (var u : users) {
System.out.printf("%s %s %s %s %s\n", u.getId(), u.getName(), u.getNick(), u.getPasswd(),
u.getCreatedAt());
}
users = db.find(User.class, Q.eq_("nick"), "nick2"); // 条件查询
System.out.println(users.size());
var setters = new HashMap<String, Object>();
setters.put("passwd", "whatever");
db.update(User.class, setters, 2); // 修改
users = db.find(User.class); // 再列出所有行
System.out.println(users.size());
for (var u : users) {
System.out.printf("%s %s %s %s %s\n", u.getId(), u.getName(), u.getNick(), u.getPasswd(),
u.getCreatedAt());
}
db.delete(User.class, 1); // 删除
db.delete(User.class, 2); // 再删除
count = db.count(User.class); // 统计所有行
System.out.println(count);
} finally {
db.drop(User.class); // 删除表
}
}
}单表复合主键增删改查
public class DemoCompoundPk {
private final static String URI = "jdbc:mysql://localhost:3306/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8";
public static void main(String[] args) {
var db = new DemoDB("demo", URI);
try {
db.create(Member.class); // 建表
var member = new Member(1, 2, "boss", null);
db.insert(member); // 插入
member = db.get(Member.class, 1, 2); // 主键查询
System.out.println(member.getTitle());
member = new Member(2, 2, "manager", new Date());
db.insert(member); // 再插入
var count = db.count(Member.class); // 获取总行数
System.out.println(count);
var members = db.find(Member.class); // 获取全部行
for (var m : members) {
System.out.printf("%d %d %s %s\n", m.getUserId(), m.getGroupId(), m.getTitle(), m.getCreatedAt());
}
member = new Member(2, 3, "manager", new Date());
db.insert(member); // 再插入
members = db.find(Member.class, Q.eq_("group_id"), 2); // 条件查询
for (var m : members) {
System.out.printf("%d %d %s %s\n", m.getUserId(), m.getGroupId(), m.getTitle(), m.getCreatedAt());
}
var setters = new HashMap<String, Object>();
setters.put("title", "employee");
db.update(Member.class, setters, 2, 3); // 修改
member = db.get(Member.class, 2, 3); // 主键查询
System.out.println(member.getTitle());
db.delete(Member.class, 1, 2); // 删除
db.delete(Member.class, 2, 2); // 删除
db.delete(Member.class, 2, 3); // 删除
count = db.count(Member.class); // 再获取总行数
System.out.println(count);
} finally {
db.drop(Member.class); // 删表
}
}
}复杂查询
public class DemoComplexQuery {
private final static String URI = "jdbc:mysql://localhost:3306/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8";
public static void main(String[] args) {
var db = new DemoDB("demo", URI);
try {
db.create(Exam.class); // 建表
var random = new Random();
for (var i = 0; i < 100; i++) {
var userId = Math.abs(random.nextLong());
var exam = new Exam(userId, random.nextInt(100), random.nextInt(100), random.nextInt(100),
random.nextInt(100), random.nextInt(100), random.nextInt(100));
db.insert(exam); // 插入
}
System.out.println(db.count(Exam.class)); // 查询总行数
// math >= 50
var exams = db.find(Exam.class, Q.ge_("math"), 50); // 条件查询
System.out.println(exams.size());
var count = db.count(Exam.class, Q.ge_("math"), 50); // 条件总行数
System.out.println(count);
// math > 50 & english >= 50
exams = db.find(Exam.class, Q.and(Q.gt_("math"), Q.ge_("english")), 50, 50); // 条件查询
System.out.println(exams.size());
count = db.count(Exam.class, Q.and(Q.gt_("math"), Q.ge_("english")), 50, 50); // 条件总行数
System.out.println(count);
// math > 50 || english >= 50
exams = db.find(Exam.class, Q.or(Q.gt_("math"), Q.ge_("english")), 50, 50); // 条件查询
System.out.println(exams.size());
count = db.count(Exam.class, Q.or(Q.gt_("math"), Q.ge_("english")), 50, 50); // 条件总行数
System.out.println(count);
// math > 50 && (english >= 50 || chinese > 60)
exams = db.find(Exam.class, Q.and(Q.gt_("math"), Q.or(Q.ge_("english"), Q.gt_("chinese"))), 50, 50, 60); // 条件查询
System.out.println(exams.size());
count = db.count(Exam.class, Q.and(Q.gt_("math"), Q.or(Q.ge_("english"), Q.gt_("chinese"))), 50, 50, 60); // 条件总行数
System.out.println(count);
// math > 50 || physics between 60 and 80 || chemistry < 60
exams = db.find(Exam.class, Q.or(Q.gt_("math"), Q.between_("physics"), Q.lt_("chemistry")), 50, 60, 80, 60); // 条件查询
System.out.println(exams.size());
count = db.count(Exam.class, Q.or(Q.gt_("math"), Q.between_("physics"), Q.lt_("chemistry")), 50, 60, 80,
60); // 条件总行数
System.out.println(count);
// group by math / 10
var q = Q.select().field("(math div 10) * 10 as mathx", "count(1)").table("exam").groupBy("mathx")
.having(Q.gt_("count(1)")).orderBy("count(1)", "desc"); // 复杂sql构造
var rank = new LinkedHashMap<Integer, Integer>();
db.any(Exam.class, q, stmt -> { // 原生sql查询
stmt.setInt(1, 0);
ResultSet rs = stmt.executeQuery();
while (rs.next()) {
rank.put(rs.getInt(1), rs.getInt(2));
}
return rs;
});
rank.forEach((mathx, c) -> {
System.out.printf("[%d-%d) = %d\n", mathx, mathx + 10, c);
});
} finally {
db.drop(Exam.class);
}
}
}分表
public class DemoPartitioning {
private final static String URI = "jdbc:mysql://localhost:3306/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8";
public static void main(String[] args) {
var db = new DemoDB("demo", URI);
try {
for (int i = 0; i < BookShelf.PARTITIONS; i++) {
db.create(BookShelf.class, String.valueOf(i)); // 创建所有分表
}
var bss = new ArrayList<BookShelf>();
for (int i = 0; i < 100; i++) {
var bs = new BookShelf("user" + i, "book" + i, "comment" + i, new Date());
bss.add(bs);
db.insert(bs); // 插入，自动插入相应分表
}
for (int i = 0; i < BookShelf.PARTITIONS; i++) {
System.out.printf("partition %d count %d\n", i, db.count(BookShelf.class, String.valueOf(i)));
}
Random random = new Random();
for (var bs : bss) {
bs.setComment("comment_update_" + random.nextInt(100));
db.update(bs); // 更新，自动更新相应分表数据
}
bss = new ArrayList<BookShelf>();
for (int i = 0; i < BookShelf.PARTITIONS; i++) {
bss.addAll(db.find(BookShelf.class, String.valueOf(i))); // 指定分表列出所有行
}
for (var bs : bss) {
System.out.println(bs.getComment());
}
for (var bs : bss) {
db.delete(bs); // 挨个删除，自动删除相应分表数据
}
} finally {
for (int i = 0; i < BookShelf.PARTITIONS; i++) {
db.drop(BookShelf.class, String.valueOf(i)); // 删除所有分表
}
}
}
}分库
public class DemoSharding {
private static DemoDB[] dbs = new DemoDB[3];
static {
Map<Class<? extends IEntity>, Meta> metas = new HashMap<>();
dbs[0] = new DemoDB("demo-0", metas,
"jdbc:mysql://localhost:3306/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8");
dbs[1] = new DemoDB("demo-1", metas,
"jdbc:mysql://localhost:3307/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8");
dbs[2] = new DemoDB("demo-2", metas,
"jdbc:mysql://localhost:3308/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8");
}
public static void main(String[] args) {
var grid = new GridDemoDB(dbs); // 构造Grid实例
try {
for (int k = 0; k < BookShelf.PARTITIONS; k++) {
grid.create(BookShelf.class, String.valueOf(k)); // 创建所有分库中的分表
}
var bss = new ArrayList<BookShelf>();
for (int i = 0; i < 100; i++) {
var bs = new BookShelf("user" + i, "book" + i, "comment" + i, new Date());
bss.add(bs);
grid.insert(bs); // 插入，自动分发到相应的分库中的分表
}
for (int k = 0; k < grid.size(); k++) {
for (int i = 0; i < BookShelf.PARTITIONS; i++) {
System.out.printf("db %d partition %d count %d\n", k, i,
grid.count(BookShelf.class, k, String.valueOf(i))); // 依次查询出所有分库的分表的行数
}
}
Random random = new Random();
for (var bs : bss) {
bs.setComment("comment_update_" + random.nextInt(100));
grid.update(bs); // 更新，自动分发到相应的分库中的分表
}
for (var bs : bss) {
bs = grid.get(BookShelf.class, bs.getUserId(), bs.getBookId()); // 主键查询，自动分发到相应的分库中的分表
System.out.println(bs.getComment());
}
for (var bs : bss) {
grid.delete(bs); // 删除，自动分发到相应的分库中的分表
}
for (int k = 0; k < grid.size(); k++) {
for (int i = 0; i < BookShelf.PARTITIONS; i++) {
System.out.printf("db %d partition %d count %d\n", k, i,
grid.count(BookShelf.class, k, String.valueOf(i))); // 依次查询出所有分库的分表的行数
}
}
} finally {
for (int k = 0; k < BookShelf.PARTITIONS; k++) {
grid.drop(BookShelf.class, String.valueOf(k)); // 删除所有分库中的分表
}
}
}
}事件上下文对象
public class Context {
private DB db; // 数据库实例
private Connection conn; // 当前的链接
private Class<? extends IEntity> clazz; // 当前的实体类
private Q q; // 查询sql
private Object[] values; // 查询的绑定参数
private boolean before; // before or after
private Exception error; // 异常
private long duration; // 耗时microsecond
}事件回调
public class DemoEvent {
private final static String URI = "jdbc:mysql://localhost:3306/mydrc?user=mydrc&password=mydrc&useUnicode=true&characterEncoding=UTF8";
public static void main(String[] args) {
var db = new DemoDB("demo", URI);
db.on(ctx -> { // 全局事件回调
System.out.printf("db=%s sql=%s cost=%dus\n", ctx.db().name(), ctx.q().sql(), ctx.duration());
return true; // 返回false会导致事件链终止，后续的ORM操作也不会执行
});
try {
db.create(User.class);
db.scope(ctx -> { // 范围回调，execute方法内部的所有ORM操作都会回调
System.out.printf("db=%s sql=%s cost=%dus\n", ctx.db().name(), ctx.q().sql(), ctx.duration());
return true;
}).execute(() -> {
db.count(User.class);
db.find(User.class);
});
} finally {
db.drop(User.class); // 删除表
}
}
}本文参与 腾讯云自媒体同步曝光计划，分享自微信公众号。
原始发表：2018-04-28，如有侵权请联系 cloudcommunity@tencent.com 删除
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