JDBC练习

1.查询数据库里所有信息。

数据库sql建立数据库语句：

-- 删除tb_brand表
drop table if exists tb_brand;
-- 创建tb_brand表
create table tb_brand
(
    -- id 主键
    id           int primary key auto_increment,
    -- 品牌名称
    brand_name   varchar(20),
    -- 企业名称
    company_name varchar(20),
    -- 排序字段
    ordered      int,
    -- 描述信息
    description  varchar(100),
    -- 状态：0：禁用  1：启用
    status       int
);
-- 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0),
       ('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界', 1),
       ('小米', '小米科技有限公司', 50, 'are you ok', 1);


SELECT * FROM tb_brand;

2.创建数据对象

public class Brand {
    // id 主键
    private Integer id;
    // 品牌名称
    private String brandName;
    // 企业名称
    private String companyName;
    // 排序字段
    private Integer ordered;
    // 描述信息
    private String description;
    // 状态：0：禁用  1：启用
    private Integer status;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getBrandName() {
        return brandName;
    }

    public void setBrandName(String brandName) {
        this.brandName = brandName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    public Integer getOrdered() {
        return ordered;
    }

    public void setOrdered(Integer ordered) {
        this.ordered = ordered;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "Brand{" +
                "id=" + id +
                ", brandName='" + brandName + '\'' +
                ", companyName='" + companyName + '\'' +
                ", ordered=" + ordered +
                ", description='" + description + '\'' +
                ", status=" + status +
                '}';
    }
}

3.数据查询

package com.itheima.example;

import com.alibaba.druid.pool.DruidDataSourceFactory;
import com.itheima.pojo.Brand;
import org.junit.Test;

import javax.sql.DataSource;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

public class BrandTest {
    /**
     * 查询所有
     * 1.SQL：select * from tb_brand;
     * 2.参数：不需要
     * 3.结果:List<Brand>
     */
    @Test
    public void testSelectAll() throws Exception {
        //1.获取Connection
        //（1）加载配置文件
        Properties prop = new Properties();
        prop.load(new FileInputStream("src/druid.properties"));
        //（2）获取连接池对象
        DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
        //（3）获取数据库连接Connection
        Connection conn = dataSource.getConnection();
        //2.定义SQL
        String sql = "select * from tb_brand";
        //3.获取pstmt对象
        PreparedStatement pstmt = conn.prepareStatement(sql);
        //4.设置参数
        
        //5.执行SQL
        ResultSet rs = pstmt.executeQuery();
        
        //6.处理结果List<Brand>封装Brand对象，装载List集合
        
        Brand brand = new Brand();
        List<Brand> brands = new ArrayList<>();
        while (rs.next()){
            //（1）获取数据
            int id = rs.getInt("id");
            String brandName = rs.getString("brand_name");
            String companyName = rs.getString("company_name");
            int ordered = rs.getInt("ordered");
            String description = rs.getString("description");
            int status = rs.getInt("status");
            //（2）封装Brand对象
            brand = new Brand();
            brand.setId(id);
            brand.setBrandName(brandName);
            brand.setCompanyName(companyName);
            brand.setOrdered(ordered);
            brand.setDescription(description);
            brand.setStatus(status);
            //（3）装载集合
            brands.add(brand);
        }
        System.out.println(brands);
        
        //7.释放资源
        rs.close();
        pstmt.close();
        conn.close();
//        System.out.println(System.getProperty("user.dir"));  //查询文件目录位置
    }
}

4.druid配置文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:13306/brand?useSSL=false&useServerPrepStmts=true
username=root
password=zyhhkb58422
# 初始化连接数量
initialSize=5
# 最大连接数
maxActive=10
# 最大等待时间
maxWait=3000tb_brand

    /** 添加
     * 1.SQL:insert into tb_brand(brand_name,company_name,ordered,description,status)values(?,?,?,?,?);
     * 2.参数:需要，除了id之外的所有参数信息
     * 3.结果:boolean
     */
    @Test
    public void testAdd() throws Exception {
        // 接收页面提交的参数
        String brandName = "香飘飘";
        String companyName = "香飘飘";
        int ordered = 1;
        String description = "绕地球一圈";
        int status = 1;
        //1.获取Connection
        //（1）加载配置文件
        Properties prop = new Properties();
        prop.load(new FileInputStream("src/druid.properties"));
        //（2）获取连接池对象
        DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
        //（3）获取数据库连接Connection
        Connection conn = dataSource.getConnection();
        //2.定义SQL
        String sql = "insert into tb_brand(brand_name,company_name,ordered,description,status)values(?,?,?,?,?);";
        //3.获取pstmt对象
        PreparedStatement pstmt = conn.prepareStatement(sql);
        //4.设置参数
        pstmt.setString(1,brandName);
        pstmt.setString(2,companyName);
        pstmt.setInt(3,ordered);
        pstmt.setString(4,description);
        pstmt.setInt(5,status);
        //5.执行SQL
        int count = pstmt.executeUpdate();
        //6.处理结果
        System.out.println(count > 0);
        //7.释放资源
        pstmt.close();
        conn.close();
    }
    /**
     * 修改
     * 1.SQL:
     update tb_brand
     set brand_name = ?,
     company_name = ?,
     ordered = ?,
     description = ?,
     status = ?
     where id = ?
     * 2.参数:需要，所有参数信息
     * 3.结果:boolean
     */
    @Test
    public void testUpdate() throws Exception {
        // 接收页面提交的参数
        String brandName = "香飘飘";
        String companyName = "香飘飘";
        int ordered = 1000;
        String description = "绕地球三圈";
        int status = 1;
        int id = 4;
        //1.获取Connection
        //（1）加载配置文件
        Properties prop = new Properties();
        prop.load(new FileInputStream("src/druid.properties"));
        //（2）获取连接池对象
        DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
        //（3）获取数据库连接Connection
        Connection conn = dataSource.getConnection();
        //2.定义SQL
        String sql = "update tb_brand\n" +
                "     set brand_name = ?,\n" +
                "     company_name= ?,\n" +
                "     ordered = ?,\n" +
                "     description = ?,\n" +
                "     status = ?\n" +
                "     where id = ?";
        //3.获取pstmt对象
        PreparedStatement pstmt = conn.prepareStatement(sql);
        //4.设置参数
        pstmt.setString(1,brandName);
        pstmt.setString(2,companyName);
        pstmt.setInt(3,ordered);
        pstmt.setString(4,description);
        pstmt.setInt(5,status);
        pstmt.setInt(6,id);
        //5.执行SQL
        int count = pstmt.executeUpdate();
        //6.处理结果
        System.out.println(count > 0);
        //7.释放资源
        pstmt.close();
        conn.close();
    }
    /** 删除
     * 1.SQL:delete from tb_brand where id = ?;
     * 2.参数:需要，id的参数信息
     * 3.结果:boolean
     */
    @Test
    public void testDelete() throws Exception {
        // 接收页面提交的参数
        int id = 4;
        //1.获取Connection
        //（1）加载配置文件
        Properties prop = new Properties();
        prop.load(new FileInputStream("src/druid.properties"));
        //（2）获取连接池对象
        DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
        //（3）获取数据库连接Connection
        Connection conn = dataSource.getConnection();
        //2.定义SQL
        String sql = "delete from tb_brand where id = ?;";
        //3.获取pstmt对象
        PreparedStatement pstmt = conn.prepareStatement(sql);
        //4.设置参数
        pstmt.setInt(1,id);
        //5.执行SQL
        int count = pstmt.executeUpdate();
        //6.处理结果
        System.out.println(count > 0);
        //7.释放资源
        pstmt.close();
        conn.close();
    }
}

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