java开发之Java ORM 框架推荐

1 前言
ObjectiveSQL 是一个Java ORM 框架，它不仅是Active Record 模式在Java 中的应用，同时还针对复杂SQL 编程提供近乎完美的解决方案，java培训使得Java 代码与SQL 语句有机的结合，改变了传统SQL 的编程模型（以字符串拼接为主的编程模型）。

ObjectiveSQL 项目分为两部分：一部分是运行期Maven 依赖 objective-sql 或 objsql-springboot，主要实现了基础的ORM 特性和SQL 编程模型，另一部分是IntelliJ IDEA 插件，兼容Java 运算符重载和动态代码提示。

ObjectiveSQL 主要解决：

动态代码生成：基于领域模型（Domain Model），自动生成简单SQL 编程代码，使应用系统开发只关注自身的业务特性，提升开发效率
可编程SQL：将SQL 中的控制原语、谓词、函数以及过程化逻辑等抽象为Java 中的高级类型，与Java 融为一体，使得SQL 成为真正过程化、逻辑型编程语言，可封装、可复用以及单元测试
表达式语法一致性：Java 语法与SQL 语法等价替换，包括：数学计算、函数调用、比较与逻辑计算表达式，Java 表达式可以直接转换为SQL 表达式。
2 依赖安装
2.1 IntelliJ IDEA 插件安装
Preferences/Settings -> Plugins -> Search with "ObjectiveSql" in market -> Install

2.2 Maven 集成
独立应用程序，请将下列代码添加至dependencies：

<!-- In standalone -->
<dependency>

<groupId>com.github.braisdom</groupId>
<artifactId>objective-sql</artifactId>
<version>{objsql.version}</version>

</dependency>

Spring Boot 集成项目，请将下列代码添加至dependencies：

<!-- In Spring Boot, you need add spring-jdbc dependency before -->
<dependency>
<groupId>com.github.braisdom</groupId>
<artifactId>objsql-springboot</artifactId>
<version>{objsql.version}</version>
</dependency>
最新版本请访问 ObjectiveSQL，ObjSqlSpringBoot

2.3 Maven Compiler 参数配置
请将下列代码添加至pom.xml 中的 <build> / <plugins> 结点下：

<plugin>

<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<configuration>
    <source>8</source>
    <target>8</target>
    <encoding>UTF-8</encoding>
    <compilerArgs>
        <arg>-Xplugin:JavaOO</arg>
    </compilerArgs>
    <annotationProcessorPaths>
        <path>
            <groupId>com.github.braisdom</groupId>
            <artifactId>objective-sql</artifactId>
            <version>${objsql.version}</version>
        </path>
    </annotationProcessorPaths>
</configuration>

</plugin>

3 数据库连接注入
3.1 独立应用系统
以MySQL 为例，基于 ConnectionFactory 构造数据连接获取逻辑，并将其注入Databases。

private static class MySQLConnectionFactory implements ConnectionFactory {

@Override
public Connection getConnection(String dataSourceName) throws SQLException {
    try {
        String url = "jdbc:mysql://localhost:4406/objective_sql";
        String user = "root";
        String password = "******";
        return DriverManager.getConnection(url, user, password);
    } catch (SQLException e) {
        throw e;
    } catch (Exception e) {
        throw new IllegalStateException(e.getMessage(), e);
    }
}

}

Databases.installConnectionFactory(new MySQLConnectionFactory());
getConnection 方法中的的 dataSourceName 参数仅在多数据源的场景下使用，getConnection 方法可以根据不同的 dataSourceName 返回不同的数据库连接，其它场景下可以忽略该参数。

3.2 集成Spring Boot
应用系统基于Spring Boot 框架开发时，无需手动注入数据源，请按下列方法进行配置即可：

spring:
profiles:

name: objective-sql-example
active: development

datasource:

driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:4406/objective_sql
username: root
password: ******
hikari:
  idle-timeout: 10000
  maximum-pool-size: 10
  minimum-idle: 5
  pool-name: Master

# Configurations for multiple databases
extensions:
  # The name of data source, which will match with @DomainModel definition 
  slave:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:4406/objective_sql
    username: root
    password: ******
    hikari:
      idle-timeout: 10000
      maximum-pool-size: 10
      minimum-idle: 5
      pool-name: Slave

其中 extensions 标记仅当多数据源时需要配置，而slave 作为数据源名称，应该与DomainModel 中定义的数据源名称匹配，或者通过DomainModelDescriptro 中动态数据源名称匹配。

4 简单SQL 编程指南
ObjectiveSQL 提供的简单SQL 编程主要针对单表的相关SQL 使用，通过动态生成的Java API 为应用系统的开发提供便捷的开发体验。

4.1 命名约定
4.1.1 类名与表名
缺省情况下，ObjectiveSQL 以驼峰与下划线的形式对Java 元素与数据库元素进行互相转换，示例如下：

1）Java 定义如下：

class Member {

    private String memberNo;
private String name;

}
2）数据库表定义如下：

create table members (

    member_no varchar not null,
name varchar

);
类名：Member 在数据库中对应的名称为 members，而字段名memberNo 对应的列名为 member_no，而字段名name 没有任何变化

4.1.1 关联对象
1）Java 定义如下：

class Member {

    private String memberNo;
private String name;

@Relation(relationType = RelationType.HAS_MANY)
private List<Order> orders;

}

class Order {

    private String no;
private Long memberId;

@Relation(relationType = RelationType.BELONGS_TO)
private Member member;

}
2）数据库表定义如下：

create table members (

    member_no varchar not null,
name varchar

);

create table members (

    member_no varchar not null,
member_id int(10) not null,
name varchar

);
通过上面的结构定义，可以看出几个关键特征：

用于承载HAS_MANY 关联对象的实例变量members 是由类型转换成复数，而BELONGS_TO 与HAS_ONE则为单数
Order 类中存在一个外键对应的实例变量memberId，同时在表中也存在一个member_id与其对应
其它规则与类与表转换的规则一致
注意：所有类名在转换为复杂时，遵循英文的规律，例如：person 对应 pepole

4.2 领域模型定义
@DomainModel
public class Member {

@Size(min = 5, max = 20)
private String no;

@Queryable
private String name;
private Integer gender;
private String mobile;

@Transient
private String otherInfo;

@Relation(relationType = RelationType.HAS_MANY)
private List<Order> orders;

}

ObjectiveSQL 会根据上述模型定义，自动生成基础的SQL 编程相关方法和SQL 抽象模型定义

4.3 数据查询
Member.countAll();
Member.count("name = ?", "braisdom");

Member.queryByPrimaryKey(1);
Member.queryFirst("id > ?", 1);
Member.query("id > ?", 1);
Member.queryAll();

4.4 数据更新
Member.create(newMember);
Member.create(newMember, true); // Create a member without validating
Member.create(Member.newInstanceFrom(memberHash));
Member.create(new Member[]{newMember1, newMember2, newMember3}, false);

Member.update(1L, newMember, true); // Update a member by primary key and skip validationg
Member.update("name = ?", "name = ?", newName, oldName);

Member.destroy(1L); // Delete a member by primary key
Member.destroy("name = ?", "Mary");

4.5 事务
4.5.1 基于Annotation 的事务
// The method will be executed in a database thransaction
@Transactional
public static void makeOrder(Order order, OrderLine... orderLines) throws SQLException {
Order.create(order, false);
OrderLine.create(orderLines, false);
}

4.5.2 手动事务管理
// Transaction executing manually
Databases.executeTransactionally(((connection, sqlExecutor) -> {

  Member.update(1L, newMember, true);
  Member.update("name = ?", "name = ?", newName, oldName);
return null;

}));
4.6 关联对象查询
Member.queryAll(Member.HAS_MANY_ORDERS);
Member.queryFirst("id > ?", Member.HAS_MANY_ORDERS, 1);
Member.query("id > ?", Member.HAS_MANY_ORDERS, 1);

Member.queryByPrimaryKey(1, Member.HAS_MANY_ORDERS);
Member.queryByName("braisdom", Member.HAS_MANY_ORDERS);

上述代码中的 Member.HAS_MANY_ORDERS 属性为ObjectiveSQL 自动生成，在特殊情况下，可以基于 com.github.braisdom.objsql.relation.Relationship 自定义关联关系的构建逻辑。

4.7 分页查询
// Create a Page instance with current page and page size
Page page = Page.create(0, 10);
PagedList<Member> members = Member.pagedQueryAll(page, Member.HAS_MANY_ORDERS);
PagedList<Member> members = Member.pagedQuery(page, "name = ?", "braisdom");

4.8 Query 接口编程
Query query = Member.createQuery();
query.project("name").groupBy("name").having("COUNT(*) > 0").orderBy("name DESC");

List<Member> members = query.execute(Member.HAS_MANY_ORDERS);

// Paged querying with querying dynamically
Paginator paginator = Databases.getPaginator();
Page page = Page.create(0, 10);
PagedList<Member> pagedMembers = paginator

                  .paginate(page, query, Member.class, Member.HAS_MANY_ORDERS);

针对SQL 中的分组和排序，需要通过Query 接口完成，同时Query 接口也可以进行分页和关联对象查询。

4.9 Validation
ObjectiveSQL Validation 内部集成了Jakarta Bean Validation

4.9.1 手工调用 validate 方法
Member newMember = new Member()

    .setNo("100")
    .setName("Pamela")
    .setGender(1)
    .setMobile("15011112222");

// Violations occurred in field 'no'
Validator.Violation[] violations = newMember.validate();

4.9.2 创建对象时 validate
Member newMember = new Member()

    .setNo("100000")
    .setName("Pamela")
    .setGender(1)
    .setMobile("15011112222");

Member.create(newMember);
Member.create(newMember, true); // Skip validation

4.10 自定义SQL
Member.execute("DELETE FROM members WHERE name = ?", "Pamela");

5 复杂SQL 编程指南
ObjectiveSQL 提供的复杂SQL 编程，其实是对SQL 语法的一种抽象和建模，以Java API 形式进行互相作用，使得复杂SQL 不再以字符串的形式出现在Java 中，从而实现动态化SQL 变得清晰易理解，不同的业务系统也可以基于ObjectiveSQL 对自身业务的再抽象和建模，实现SQL 逻辑的复用。

5.1 JOIN 查询
5.1.1 隐式 Join
Member.Table member = Member.asTable();
Order.Table order = Order.asTable();

Select select = new Select();

select.project(member.no, member.name, count().as("order_count"))

    .from(member, order)
    .where(member.id.eq(order.memberId))
    .groupBy(member.no, member.name);

List<Member> members = select.execute(Member.class);

SELECT T0.NO , T0.name , COUNT(*) AS order_count
FROM members AS T0, orders AS T1
WHERE (T0.id = T1.member_id )
GROUP BY T0.NO , T0.name

5.1.2 显式Join
Member.Table member = Member.asTable();
Order.Table order = Order.asTable();

Select select = new Select();

select.project(member.no, member.name, count().as("order_count"))

    .from(member)
    .leftOuterJoin(order, order.memberId.eq(member.id))
    .groupBy(member.no, member.name);

List<Member> members = select.execute(Member.class);

SELECT T0.NO , T0.name , COUNT(*) AS order_count
FROM members AS T0
LEFT OUTER JOIN orders AS T1 ON (T1.member_id = T0.id )
GROUP BY T0.NO , T0.name

5.2 分页查询
Member.Table member = Member.asTable();
Order.Table order = Order.asTable();

Paginator<Member> paginator = Databases.getPaginator();
Page page = Page.create(0, 20);

Select select = new Select();

select.project(member.no, member.name, count().as("order_count"))

    .from(member, order)
    .where(member.id.eq(order.memberId))
    .groupBy(member.no, member.name);

PagedList<Member> members = paginator.paginate(page, select, Member.class);

-- Counting SQL
SELECT COUNT(*) AS count_
FROM (

SELECT
    `T0`.`NO`,
    `T0`.`name`,
    COUNT(*) AS `order_count`
FROM `members` AS `T0`, `orders` AS `T1`
WHERE (`T0`.`id` = `T1`.`member_id`)
GROUP BY `T0`.`NO`, `T0`.`name`

) T

-- Querying SQL
SELECT T0.NO, T0.name, COUNT(*) AS order_count
FROM members AS T0, orders AS T1
WHERE (T0.id = T1.member_id)
GROUP BY T0.NO, T0.name
LIMIT 0, 20

5.3 复杂表达式查询
ObjectiveSQL 通过运算符重域技术使得Expression 也可以参与各类运算符计算，从而使得Java 代码变得简单易懂，而不是通过各类运算符方法进行计算。ObjectiveSQL 表达式计算时并不能够与SQL 表达完匹配，默认情况下所有表达式均可以进行算术运算，在IntelliJ IDEA 中并不能给出完整的提醒，例如：JoinExpression 也可以进行算术运算，此时在IntelliJ IDEA 中并不会出现语法错误的提醒，但在执行运算过程中会抛出 UnsupportedArithmeticalException，该异常为RuntimeException 的子类。

Order.Table orderTable = Order.asTable();
Select select = new Select();

select.project((sum(orderTable.amount) / sum(orderTable.quantity) * 100).as("unit_amount"))

    .from(orderTable)
    .where(orderTable.quantity > 30 &&
            orderTable.salesAt.between("2020-05-01 00:00:00", "2020-05-02 23:59:59"))
    .groupBy(orderTable.memberId);

List<Order> orders = select.execute(Order.class);
SELECT ((((SUM(T0.amount ) / SUM(T0.quantity ) )) * 100)) AS unit_amount
FROM orders AS T0
WHERE ((T0.quantity > 30)

AND `T0`.`sales_at` BETWEEN '2020-05-01 00:00:00' AND '2020-05-02 23:59:59' )

GROUP BY T0.member_id

5.4 动态查询
所谓动态查询，实际上就是表达式的构建过程跟随着参数的有无而变化，基于这种使用场景，ObjectiveSQL 设计了一个永真的逻辑表达式EternalExpression ，永真表达式是程序上的一种巧妙设计，使得代码逻辑变得更清晰，即使所有参数均未赋值，整个表达式也会存在一个永的表达，确保最终SQL 语句的正常。

String[] filteredNo = {"202000001", "202000002", "202000003"};
int filteredQuantity = 0;

Order.Table orderTable = Order.asTable();
Select select = new Select();
LogicalExpression eternalExpression = new EternalExpression();

if(filteredNo.length > 0) {

eternalExpression = eternalExpression.and(orderTable.no.in(filteredNo));

}

if(filteredQuantity != 0) {

eternalExpression = eternalExpression.and(orderTable > filteredQuantity);

}

select.project((sum(orderTable.amount) / sum(orderTable.quantity) * 100).as("unit_amount"))

    .from(orderTable)
    .where(eternalExpression)
    .groupBy(orderTable.memberId);

List<Order> orders = select.execute(Order.class);

SELECT ((((SUM(T0.amount ) / SUM(T0.quantity ) )) * 100)) AS unit_amount
FROM orders AS T0
WHERE ((1 = 1) AND T0.NO IN ('202000001', '202000002', '202000003') )
GROUP BY T0.member_id

6 高级使用
6.1 日志集成
由于 ObjectiveSQL 无法决定应用系统使用哪一个日志框架，所以ObjectiveSQL 并未集成任何第三方日志框架，确认使用JDK 自身的日志框架，如果应用系统需要使用自身的日志框架，并在系统启动完成后注入ObjectiveSQL，请按下列方式集成（以Slf4j 为例）。

6.1.1 LoggerFactory 扩展实现
public class ObjLoggerFactoryImpl implements LoggerFactory {

private class ObjLoggerImpl implements Logger {

    private final org.slf4j.Logger logger;

    public ObjLoggerImpl(org.slf4j.Logger logger) {
        this.logger = logger;
    }

    @Override
    public void debug(long elapsedTime, String sql, Object[] params) {
        logger.debug(createLogContent(elapsedTime, sql, params));
    }

    @Override
    public void info(long elapsedTime, String sql, Object[] params) {
        logger.info(createLogContent(elapsedTime, sql, params));
    }

    @Override
    public void error(String message, Throwable throwable) {
        logger.error(message, throwable);
    }

    private String createLogContent(long elapsedTime, String sql, Object[] params) {
        String[] paramStrings = Arrays.stream(params)
                .map(param -> String.valueOf(param)).toArray(String[]::new);
        String paramString = String.join(",", paramStrings);
        return String.format("[%dms] %s, with: [%s]",
                elapsedTime, sql, String.join(",",
                paramString.length() > 100 ? StringUtil
                        .truncate(paramString, 99) : paramString));
    }
}

@Override
public Logger create(Class<?> clazz) {
    org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(clazz);
    return new ObjLoggerImpl(logger);
}

}

6.1.1 普通应用程序注入方式
public class Application {

public static void main(String[] args) {
    Databases.installLoggerFactory(new ObjLoggerFactoryImpl());
    // others
}

}

6.1.2 Spring Boot 应用程序注入方式
@SpringBootApplication
@EnableAutoConfiguration
public class Application {

public static void main(String[] args) {
    SpringApplication springApplication = new SpringApplication(Application.class);
    springApplication.addListeners(new ApplicationListener<ApplicationReadyEvent>() {

        @Override
        public void onApplicationEvent(ApplicationReadyEvent event) {
            Databases.installLoggerFactory(new ObjLoggerFactoryImpl());
        }
    });
    springApplication.run(args);
}

}

6.2 基于SQL 语句的对象缓存
应用系统中对时间性不强的数据会进行数据缓存，通常会将数据缓存至Redis 中，针对些特性，可以扩展ObjectiveSQL 的 SQLExecutor 接口轻易实现。

6.1.1 SQLExecutor 扩展实现
public class CacheableSQLExecutor<T> extends DefaultSQLExecutor<T> {

private static final List<Class<? extends Serializable>> CACHEABLE_CLASSES =
        Arrays.asList(new Class[]{Member.class});
private static final Integer CACHED_OBJECT_EXPIRED = 60;
private static final String KEY_SHA = "SHA";

private Jedis jedis = new Jedis("localhost", 6379);
private MessageDigest messageDigest;

public CacheableSQLExecutor() {
    try {
        messageDigest = MessageDigest.getInstance(KEY_SHA);
    } catch (NoSuchAlgorithmException e) {
        throw new IllegalArgumentException(e.getMessage(), e);
    }
}

@Override
public List<T> query(Connection connection, String sql,
                     TableRowAdapter tableRowAdapter, Object... params) 
  throws SQLException {
    Class<?> domainClass = tableRowAdapter.getDomainModelClass();

    if (CACHEABLE_CLASSES.contains(domainClass)) {
        if(!Serializable.class.isAssignableFrom(domainClass)) {
            throw new IllegalArgumentException(String
                                               .format("The %s cannot be serialized"));
        }

        messageDigest.update(sql.getBytes());

        String hashedSqlId = new BigInteger(messageDigest.digest()).toString(64);
        byte[] rawObjects = jedis.get(hashedSqlId.getBytes());

        if (rawObjects != null) {
            return (List<T>) SerializationUtils.deserialize(rawObjects);
        } else {
            List<T> objects = super.query(connection, sql, tableRowAdapter, params);
            byte[] encodedObjects = SerializationUtils.serialize(objects);
            SetParams expiredParams = SetParams.setParams().ex(CACHED_OBJECT_EXPIRED);

            jedis.set(hashedSqlId.getBytes(), encodedObjects, expiredParams);

            return objects;
        }
    }
    return super.query(connection, sql, tableRowAdapter, params);
}

}

6.1.1 注入方式
public class Application {

public static void main(String[] args) {
    Databases.installSqlExecutor(new CacheableSQLExecutor());
    // others
}

}

Spring Boot 的注入方式去 LogFactory 的注入方式相同

6.3 ColumnTransition 扩展
ColumnTransition 是ObjectiveSQL 对外提供的一种数据类型转的扩展接口，该接口的详细定义请参考：ColumnTransition.java ，以日期形式为例，介绍ColumnTransition 的扩展方式。

public class SqlDateTimeTransition<T> implements ColumnTransition<T> {

@Override
public Object sinking(DatabaseMetaData databaseMetaData, T object,
                      TableRowAdapter tableRowDescriptor, 
                      String fieldName, FieldValue fieldValue) 
  throws SQLException {
    String databaseName = databaseMetaData.getDatabaseProductName();
    if (fieldValue != null && fieldValue.getValue() != null) {
        if (SQLite.equals(databaseName) || Oracle.equals(databaseName)) {
            return fieldValue;
        } else if (PostgreSQL.equals(databaseName)) {
            if (fieldValue.getValue() instanceof Timestamp) {
                return fieldValue.getValue();
            } else if (fieldValue.getValue() instanceof Long) {
                Instant value = Instant.ofEpochMilli((Long) fieldValue.getValue());
                return Timestamp.from(value);
            } else {
                return Timestamp.valueOf(String.valueOf(fieldValue.getValue()));
            }
        } else {
            return fieldValue;
        }
    }
    return null;
}

@Override
public Object rising(DatabaseMetaData databaseMetaData, 
                     ResultSetMetaData resultSetMetaData,
                     T object, TableRowAdapter tableRowDescriptor, 
                     String columnName, Object columnValue) throws SQLException {
    String databaseName = databaseMetaData.getDatabaseProductName();
    try {
        if (columnValue != null) {
            if (SQLite.equals(databaseName)) {
               Instant value = Instant
                 .ofEpochMilli(Long.valueOf(String.valueOf(columnValue)))
                return Timestamp.from(value);
            } else {
                return columnValue;
            }
        }
    } catch (DateTimeParseException ex) {
        String message = String.format("Invalid raw DataTime of '%s' from database: %s",
                columnName, columnValue);
        throw new IllegalArgumentException(message, ex);
    }
    return null;
}

}

sinking 方法是将Java 中的值，转换为数据库所能接受的值，rising则为将数据库中的值，转换为Java 所能接受的值。

文章转自：架构师必备