这是IStudentDao

public interface IStudentDao {
// 保存数据
void save(Studentinfo stu);

// 修改指定学生信息
void update(Integer studentId, Studentinfo stu);

// 删除学生
void delete(int studentId);

// 获取指定学生
Studentinfo get(int studentId);

// 获取所有的学生
List<Studentinfo> getAll();

}

这是StudentinfoDaoImpl

public class StudentinfoDaoImpl implements IStudentDao {

// 增
@Override
public void save(Studentinfo stu) {
String sql = "insert into studentInfo(studentName,studentAge) values(?,?)";
QueryRunner qr = new QueryRunner(JDBCUtil.getDS());
try {
qr.update(sql, stu.getStudentName(), stu.getStudentAge());
} catch (SQLException e) {
e.printStackTrace();
}
}

// 改---<有问题>
@Override
public void update(Integer studentId, Studentinfo stu) {
String sql = "update studentinfo set studentName=?,studentAge=? where studentId=?";
QueryRunner qr = new QueryRunner(JDBCUtil.getDS());
try {
qr.update(sql, stu.getStudentName(), stu.getStudentAge(), stu.getStudentId());
} catch (SQLException e) {
e.printStackTrace();
}
}

// 删
@Override
public void delete(int studentId) {
String sql = "delete from studentinfo where studentId=?";
QueryRunner qr = new QueryRunner(JDBCUtil.getDS());
try {
qr.update(sql, studentId);
} catch (SQLException e) {
e.printStackTrace();
}
}

// 查-单一条件
@Override
public Studentinfo get(int studentId) {

    String sql = "select * from studentinfo where studentId=?";
    QueryRunner qr = new QueryRunner(JDBCUtil.getDS());
    try {
        return qr.query(sql, new BeanHandler<Studentinfo>(Studentinfo.class), studentId);
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return null;
}

// 查-全部信息
@Override
public List<Studentinfo> getAll() {

    String sql = "select * from studentinfo ";
    QueryRunner qr = new QueryRunner(JDBCUtil.getDS());
    try {
        return qr.query(sql, new BeanListHandler<Studentinfo>(Studentinfo.class));
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return null;
}

}

这是Studentinfo

package com.zixue.jdbc.domain;

public class Studentinfo {
private Integer studentId;
private String studentName;
private Integer studentAge;

public Integer getStudentId() {
    return studentId;
}

public void setStudentId(Integer studentId) {
    this.studentId = studentId;
}

public String getStudentName() {
    return studentName;
}

public void setStudentName(String studentName) {
    this.studentName = studentName;
}

public Integer getStudentAge() {
    return studentAge;
}

public void setStudentAge(Integer studentAge) {
    this.studentAge = studentAge;
}

// 无参公共构造器

public Studentinfo() {
    super();
}

@Override
public String toString() {
    return "Studentinfo [studentId=" + studentId + ", studentName=" + studentName + ", studentAge=" + studentAge
            + "]";
}

}

这是StudentinfoDaoTest 测试类：其中update更新不成功？

package com.zixue.jdbc.test;

import java.util.List;

import org.junit.Test;

/**

• @ClassName: StudentinfoDaoTest
• @Description:Junit测试类
• @author: sadfoo2019
• @date: 2019年11月11日 下午8:19:59
• @Copyright:
  */
  public class StudentinfoDaoTest {
  // 增
  @Test
  public void save() {
  Studentinfo si = new Studentinfo();
  si.setStudentName("王1黑");
  si.setStudentAge(22);
  // 保存学生
  IStudentDao dao = new StudentinfoDaoImpl();
  dao.save(si);
  }

// 删 根据id删除信息
@Test
public void delete() {
IStudentDao dao = new StudentinfoDaoImpl();
dao.delete(2019315);
}

// 改 根据id修改信息
@Test
public void updata() {

    Studentinfo sinfo = new Studentinfo();
    sinfo.setStudentName("四大金刚");
    sinfo.setStudentAge(190);
    // 保存学生
    IStudentDao dao = new StudentinfoDaoImpl();
    dao.update(2019316, sinfo);
}

// 查 根据id查询信息
@Test
public void get() {
IStudentDao dao = new StudentinfoDaoImpl();
Studentinfo stu1 = dao.get(2019316);
System.out.println("根据id查询的学生信息：" + stu1);
}

// 查 查询全部信息
@Test
public void getAll() {
IStudentDao dao = new StudentinfoDaoImpl();
List<Studentinfo> allStudentinfos = dao.getAll();
System.out.println("查所有的学生信息：" + allStudentinfos);
}
}

这是JDBCUtil 类

package com.zixue.jdbc.util;

import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

import javax.sql.DataSource;

import com.alibaba.druid.pool.DruidDataSourceFactory;

/**

• @ClassName: JDBCUtil
• @Description:连接数据库信息
• @author: sadfoo2019
• @date: 2019年11月12日 上午7:59:37

• @Copyright:
  /
  public class JDBCUtil {
  public static DataSource ds = null;// 创建连接池
  / 静态代码块保证代码执行一次（只有类被加载到JVM时才会执行一次） /
  static {
  try {
  // 加载配置文件
  Properties pp = new Properties();
  // 加载类路径下
  pp.load(new FileInputStream("resourece/druid.properties"));
  // 创建连接池，使用配置文件中的参数
  try {
  ds = DruidDataSourceFactory.createDataSource(pp);/ 此处犯错，因为没导入德鲁伊jar包 */
  } catch (Exception e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
  }

   } catch (IOException e) {
       e.printStackTrace();
   }

  }

// 获取数据源
public static DataSource getDS() {
return ds;
}

// 这部分也是获取数据源，可以不要了，暂时保留
public static Connection getConn() {
try {

// 建立与数据库的连接
return ds.getConnection();

    } catch (Exception e) {
        e.printStackTrace();
    }

    return null;
}

// 关闭资源
public static void close(Connection conn, Statement st, ResultSet rs) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (st != null) {
try {
st.cancel();
} catch (SQLException e) {
e.printStackTrace();
}
}

    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}

}