运行环境修改

可以加上这个进行定义，你tomcat运行的端口

    <build>
        <plugins>
            <plugin>
                <!-- https://mvnrepository.com/artifact/org.apache.tomcat.maven/tomcat7-maven-plugin -->
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
                <configuration>
                    <port>8888</port>
                </configuration>
            </plugin>
        </plugins>
    </build>

获取mysql数据库数据

表：

CREATE TABLE province(   -- 创建表
    id INT PRIMARY KEY AUTO_INCREMENT,
    NAME VARCHAR(20) NOT NULL
    
);
-- 插入数据
INSERT INTO province VALUES(NULL,'北京');
INSERT INTO province VALUES(NULL,'上海');
INSERT INTO province VALUES(NULL,'广州');
INSERT INTO province VALUES(NULL,'陕西');

导入mysql

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>

Items：实体类

public class Items {
    private int id;
    private String name;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

ItemsDao：

public interface ItemsDao {
    public List<Items> findAll();
}

ItemsDaoImpl：

public class ItemsDaoImpl implements ItemsDao {
    @Override
    public List<Items> findAll() {
        ArrayList<Items> list = new ArrayList<>();
        Connection connection = null;
        CallableStatement pst = null;
        ResultSet rs = null;
        try {
            //加载驱动类
            Class.forName("com.mysql.cj.jdbc.Driver");
            //先获取contection对象
            connection = DriverManager.getConnection("jdbc:mysql:///db2","root","root");
            //获取真正操作数据对象
            pst = connection.prepareCall("select * from province");
            //执行数据库查询操作
            rs = pst.executeQuery();
            //把数据库结果集转成java的List集合
            while (rs.next()){
                Items items = new Items();
                items.setId(rs.getInt("id"));
                items.setName(rs.getString("name"));
                list.add(items);
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (rs!=null){
                try {
                    rs.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }

            if (connection!=null){
                try {
                    connection.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }

            if (pst!=null){
                try {
                    pst.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }

        }
        return list;
    }
}

测试类：

public class ItemsTest {
    @Test
    public void findAll(){
        ItemsDao itemsDao = new ItemsDaoImpl();
        List<Items> list = itemsDao.findAll();
        for (Items items : list) {
            System.out.println(items.getName());
        }
    }
}

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