从JDBC开始列出10种Java从数据库中取出数据的完整过程。每种方式都包含完整的代码示例。

1. 原生JDBC

使用JDBC直接操作数据库，手动管理连接和资源。

import java.sql.*;

public class JdbcExample {

public static void main(String[] args) {

String url = "jdbc:mysql://localhost:3306/mydb";

String user = "user";

String password = "password";

try (Connection conn = DriverManager.getConnection(url, user, password);

Statement stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery("SELECT * FROM account")) {

while (rs.next()) {

int id = rs.getInt("id");

String name = rs.getString("name");

float money = rs.getFloat("money");

System.out.println("ID: " + id + ", Name: " + name + ", Money: " + money);

}

} catch (SQLException e) {

e.printStackTrace();

}

}

}

2. Spring JDBC

使用Spring的JdbcTemplate简化JDBC操作。

import org.springframework.jdbc.core.JdbcTemplate;

import org.springframework.jdbc.datasource.DriverManagerDataSource;

import javax.sql.DataSource;

import java.util.List;

import java.util.Map;

public class SpringJdbcExample {

public static void main(String[] args) {

DataSource dataSource = new DriverManagerDataSource(

"jdbc:mysql://localhost:3306/mydb", "user", "password");

JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);

List> accounts = jdbcTemplate.queryForList("SELECT * FROM account");

for (Map account : accounts) {

System.out.println("ID: " + account.get("id") +

", Name: " + account.get("name") +

", Money: " + account.get("money"));

}

}

}

3. MyBatis

使用MyBatis进行SQL映射。

（1）MyBatis配置文件（mybatis-config.xml）

（2）Mapper文件（AccountMapper.xml）

SELECT * FROM account

（3）Java代码

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.InputStream;

import java.util.List;

import java.util.Map;

public class MyBatisExample {

public static void main(String[] args) {

InputStream inputStream = MyBatisExample.class.getResourceAsStream("/mybatis-config.xml");

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

try (SqlSession session = sqlSessionFactory.openSession()) {

List> accounts = session.selectList("AccountMapper.selectAll");

for (Map account : accounts) {

System.out.println("ID: " + account.get("id") +

", Name: " + account.get("name") +

", Money: " + account.get("money"));

}

}

}

}

4. Hibernate

使用Hibernate进行ORM操作。

（1）Hibernate配置文件（hibernate.cfg.xml）

com.mysql.jdbc.Driver

jdbc:mysql://localhost:3306/mydb

user

password

org.hibernate.dialect.MySQLDialect

true

（2）实体类（Account.java）

import javax.persistence.*;

@Entity

@Table(name = "account")

public class Account {

@Id

@GeneratedValue(strategy = GenerationType.IDENTITY)

private int id;

private String name;

private float money;

// Getters and Setters

}

（3）Java代码

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import java.util.List;

public class HibernateExample {

public static void main(String[] args) {

SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

try (Session session = sessionFactory.openSession()) {

List accounts = session.createQuery("FROM Account", Account.class).list();

for (Account account : accounts) {

System.out.println("ID: " + account.getId() +

", Name: " + account.getName() +

", Money: " + account.getMoney());

}

}

}

}

5. Spring Data JPA

使用Spring Data JPA简化数据库操作。

（1）实体类（Account.java）

import javax.persistence.*;

@Entity

public class Account {

@Id

@GeneratedValue(strategy = GenerationType.IDENTITY)

private int id;

private String name;

private float money;

// Getters and Setters

}

（2）Repository接口（AccountRepository.java）

import org.springframework.data.jpa.repository.JpaRepository;

public interface AccountRepository extends JpaRepository {

}

（3）Java代码

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import java.util.List;

@SpringBootApplication

public class SpringDataJpaExample {

public static void main(String[] args) {

SpringApplication.run(SpringDataJpaExample.class, args);

}

}

@Service

class AccountService {

@Autowired

private AccountRepository accountRepository;

public void printAccounts() {

List accounts = accountRepository.findAll();

for (Account account : accounts) {

System.out.println("ID: " + account.getId() +

", Name: " + account.getName() +

", Money: " + account.getMoney());

}

}

}

6. Apache Commons DbUtils

使用DbUtils简化JDBC操作。

import org.apache.commons.dbutils.QueryRunner;

import org.apache.commons.dbutils.handlers.BeanListHandler;

import javax.sql.DataSource;

import java.util.List;

public class DbUtilsExample {

public static void main(String[] args) {

DataSource dataSource = // 初始化数据源

QueryRunner runner = new QueryRunner(dataSource);

try {

List accounts = runner.query("SELECT * FROM account",

new BeanListHandler<>(Account.class));

for (Account account : accounts) {

System.out.println("ID: " + account.getId() +

", Name: " + account.getName() +

", Money: " + account.getMoney());

}

} catch (SQLException e) {

e.printStackTrace();

}

}

}

7. JOOQ

使用JOOQ进行类型安全的SQL操作。

import org.jooq.*;

import org.jooq.impl.DSL;

import java.sql.Connection;

import java.sql.DriverManager;

public class JooqExample {

public static void main(String[] args) {

String url = "jdbc:mysql://localhost:3306/mydb";

String user = "user";

String password = "password";

try (Connection conn = DriverManager.getConnection(url, user, password)) {

DSLContext create = DSL.using(conn, SQLDialect.MYSQL);

Result result = create.select().from("account").fetch();

for (Record record : result) {

System.out.println("ID: " + record.get("id") +

", Name: " + record.get("name") +

", Money: " + record.get("money"));

}

} catch (SQLException e) {

e.printStackTrace();

}

}

}

8. Ebean

使用Ebean进行ORM操作。

import io.ebean.Ebean;

import io.ebean.EbeanServer;

import io.ebean.EbeanServerFactory;

import io.ebean.config.ServerConfig;

import java.util.List;

public class EbeanExample {

public static void main(String[] args) {

ServerConfig config = new ServerConfig();

config.setDataSourceConfig(new DataSourceConfig()

.setUrl("jdbc:mysql://localhost:3306/mydb")

.setUsername("user")

.setPassword("password"));

EbeanServer server = EbeanServerFactory.create(config);

List accounts = server.find(Account.class).findList();

for (Account account : accounts) {

System.out.println("ID: " + account.getId() +

", Name: " + account.getName() +

", Money: " + account.getMoney());

}

}

}

9. R2DBC

使用R2DBC进行响应式数据库操作。

import io.r2dbc.spi.ConnectionFactory;

import io.r2dbc.spi.ConnectionFactoryOptions;

import io.r2dbc.spi.Result;

import reactor.core.publisher.Flux;

import static io.r2dbc.spi.ConnectionFactoryOptions.*;

public class R2dbcExample {

public static void main(String[] args) {

ConnectionFactory connectionFactory = ConnectionFactories.get(ConnectionFactoryOptions.builder()

.option(DRIVER, "mysql")

.option(HOST, "localhost")

.option(PORT, 3306)

.option(USER, "user")

.option(PASSWORD, "password")

.option(DATABASE, "mydb")

.build());

Flux.from(connectionFactory.create())

.flatMap(connection -> Flux.from(connection.createStatement("SELECT * FROM account").execute()))

.flatMap(result -> result.map((row, rowMetadata) -> row.get("id") + ", " + row.get("name") + ", " + row.get("money")))

.subscribe(System.out::println);

}

}

10. JPA（Java Persistence API）

使用JPA进行ORM操作。

（1）实体类（Account.java）

import javax.persistence.*;

@Entity

public class Account {

@Id

@GeneratedValue(strategy = GenerationType.IDENTITY)

private int id;

private String name;

private float money;

// Getters and Setters

}

（2）Java代码

import javax.persistence.*;

import java.util.List;

public class JpaExample {

public static void main(String[] args) {

EntityManagerFactory emf = Persistence.createEntityManagerFactory("my-pu");

EntityManager em = emf.createEntityManager();

List accounts = em.createQuery("SELECT a FROM Account a", Account.class).getResultList();

for (Account account : accounts) {

System.out.println("ID: " + account.getId() +

", Name: " + account.getName() +

", Money: " + account.getMoney());

}

em.close();

emf.close();

}

}

总结

以上10种方式展示了从JDBC到高级ORM框架的完整数据查询过程。每种方式都有其适用场景：

JDBC：最基础，适合需要直接控制SQL的场景。

ORM框架（如Hibernate、JPA）：适合需要对象映射和简化开发的场景。

工具库（如Spring JDBC、MyBatis）：适合需要简化JDBC操作的场景。

响应式编程（如R2DBC）：适合高并发、高性能的现代应用。

根据项目需求选择合适的方式！