springboot使用druid的例子

以下是一个简单的Spring Boot项目使用Druid连接池的例子：

1. 在pom.xml中添加Druid和JDBC依赖

<dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>druid-spring-boot-starter</artifactId>
  <version>1.1.10</version>
</dependency>

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.25</version>
</dependency>

2. 在application.yml中配置Druid连接池

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC
    username: root
    password: password
    type: com.alibaba.druid.pool.DruidDataSource
    # 配置Druid连接池
    druid:
      # 初始化大小，最小，最大
      initial-size: 5
      min-idle: 5
      max-active: 20
      # 配置获取连接等待超时的时间
      max-wait: 60000
      # 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位毫秒
      time-between-eviction-runs-millis: 60000
      # 配置一个连接在池中最小生存的时间，单位毫秒
      min-evictable-idle-time-millis: 300000
      # 配置连接池中连接的使用情况，可以用来监控和统计连接池的使用情况
      log-abandoned: true
      # 配置从连接池中取出连接时是否进行有效性检查
      test-on-borrow: true
      # 配置归还连接时是否进行有效性检查
      test-on-return: false
      # 配置是否缓存preparedStatement，也就是PSCache
      pool-prepared-statements: true
      # 配置每个连接上PSCache的大小
      max-pool-prepared-statement-per-connection-size: 20
      # 配置监控统计拦截的filters
      filters: stat,wall,log4j
      # 配置DruidStatViewServlet和DruidWebStatFilter
      stat-view-servlet:
        enabled: true
        url-pattern: /druid/*
        reset-enable: false
      web-stat-filter:
        enabled: true
        url-pattern: /druid/*
        exclusions: "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*"

3. 创建一个数据访问对象（DAO）类，使用Druid连接池获取数据库连接并执行SQL查询

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import javax.annotation.PostConstruct;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

@Repository
public class UserDao {

    @Autowired
    private DruidDataSource dataSource;

    private Connection conn = null;

    @PostConstruct
    public void init() {
        try {
            conn = dataSource.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public User getUserById(int id) {
        User user = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            String sql = "SELECT * FROM users WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            rs = pstmt.executeQuery();
            if (rs.next()) {
                user = new User();
                user.setId(rs.getInt("id"));
                user.setName(rs.getString("name"));
                user.setAge(rs.getInt("age"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (rs != null) {
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (pstmt != null) {
                try {
                    pstmt.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return user;
    }
}

4. 创建一个控制器（Controller）类，使用UserDao查询数据库并返回查询结果

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

    @Autowired
    private UserDao userDao;

    @GetMapping("/users/{id}")
    public User getUserById(@PathVariable int id) {
        return userDao.getUserById(id);
    }
}

5. 运行Spring Boot应用程序并访问http://localhost:8080/users/1，应该会返回一个JSON格式的用户对象。