java实训第三天

撰写StudentDaoImpl类

package qingjiabo.student.dao.impl;
import qingjiabo.student.dbutil.ConnectionManager;
import qingjiabo.student.bean.Student;
import qingjiabo.student.dao.StudentDao;
import java.sql.*;
import java.util.ArrayList;
import java.sql.Connection;
import java.util.List;
import java.util.Vector;

public class StudentDaoImpl implements StudentDao {

@Override
public int insert(Student student) {
    // 定义插入记录数
    int count = 0;

    // 1. 获得数据库连接
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "insert into t_student (id, name, sex, age, department, class, telephone)"
            + " values (?, ?, ?, ?, ?, ?, ?)";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, student.getId());
        pstmt.setString(2, student.getName());
        pstmt.setString(3, student.getSex());
        pstmt.setInt(4, student.getAge());
        pstmt.setString(5, student.getDepartment());
        pstmt.setString(6, student.getClassname());
        pstmt.setString(7, student.getTelephone());
        // 5. 执行SQL，返回插入记录数
        count = pstmt.executeUpdate();
        // 6. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回插入记录数
    return count;
}


@Override
public int deleteById(String id) {
    // 定义删除记录数
    int count = 0;

    // 1. 获取数据库连接
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "delete from t_student where id = ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, id);
        // 5. 执行SQL，返回删除记录数
        count = pstmt.executeUpdate();
        // 6. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回删除记录数
    return count;
}

/**
 * 按班级删除学生记录
 *
 * @param clazz
 * @return 删除记录数
 */
@Override
public int deleteByClass(String clazz) {
    // 定义删除记录数
    int count = 0;

    // 1. 获取数据库连接
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "delete from t_student where class = ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, clazz);
        // 5. 执行SQL，返回删除记录数
        count = pstmt.executeUpdate();
        // 6. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回删除记录数
    return count;
}


@Override
public int deleteByDepartment(String department) {
    // 定义删除记录数
    int count = 0;

    // 1. 获得数据库连接
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "delete from t_student where department = ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, department);
        // 5. 执行SQL，返回删除记录数
        count = pstmt.executeUpdate();
        // 6. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回删除记录数
    return count;
}


public int update(Student student) {
    // 定义更新记录数
    int count = 0;

    // 1. 获得数据库连接
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "update t_student set name = ?, sex = ?, age = ?,"
            + " department = ?, class = ?, telephone = ? where id = ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, student.getName());
        pstmt.setString(2, student.getSex());
        pstmt.setInt(3, student.getAge());
        pstmt.setString(4, student.getDepartment());
        pstmt.setString(5, student.getClassname());
        pstmt.setString(6, student.getTelephone());
        pstmt.setString(7, student.getId());
        // 5. 执行SQL，返回更新记录数
        count = pstmt.executeUpdate();
        // 6. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回更新记录数
    return count;
}


@Override
public Student findById(String id) {
    // 声明学生对象
    Student student = null;

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select * from t_student where id = ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, id);
        // 5. 执行SQL，返回结果集
        ResultSet rs = pstmt.executeQuery();
        // 6. 判断结果集是否有记录
        if (rs.next()) {
            // 创建学生实体
            student = new Student();
            // 利用当前记录各字段值设置学生实体属性
            student.setId(rs.getString("id"));
            student.setName(rs.getString("name"));
            student.setSex(rs.getString("sex"));
            student.setAge(rs.getInt("age"));
            student.setDepartment(rs.getString("department"));
            student.setClassname(rs.getString("class"));
            student.setTelephone(rs.getString("telephone"));
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回学生对象
    return student;
}


@Override
public List<Student> findByName(String name) {
    // 声明学生列表
    List<Student> students = new ArrayList<Student>();

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select * from t_student where name like ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, name + "%");
        // 5. 执行SQL，返回结果集
        ResultSet rs = pstmt.executeQuery();
        // 6. 遍历结果集
        while (rs.next()) {
            // 创建学生实体
            Student student = new Student();
            // 利用当前记录各字段值设置学生实体属性
            student.setId(rs.getString("id"));
            student.setName(rs.getString("name"));
            student.setSex(rs.getString("sex"));
            student.setAge(rs.getInt("age"));
            student.setDepartment(rs.getString("department"));
            student.setClassname(rs.getString("class"));
            student.setTelephone(rs.getString("telephone"));
            // 将实体添加到学生列表
            students.add(student);
        }
        // 7. 关闭结果集
        rs.close();
        // 8. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回学生列表
    return students;
}


@Override
public List<Student> findByClass(String clazz) {
    // 声明学生列表
    List<Student> students = new ArrayList<Student>();

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select * from t_student where class like ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, clazz + "%");
        // 5. 执行SQL，返回结果集
        ResultSet rs = pstmt.executeQuery();
        // 6. 遍历结果集
        while (rs.next()) {
            // 创建学生实体
            Student student = new Student();
            // 利用当前记录各字段值设置学生实体属性
            student.setId(rs.getString("id"));
            student.setName(rs.getString("name"));
            student.setSex(rs.getString("sex"));
            student.setAge(rs.getInt("age"));
            student.setDepartment(rs.getString("department"));
            student.setClassname(rs.getString("class"));
            student.setTelephone(rs.getString("telephone"));
            // 将实体添加到学生列表
            students.add(student);
        }
        // 7. 关闭结果集
        rs.close();
        // 8. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回学生列表
    return students;
}


@Override
public List<Student> findByDepartment(String department) {
    // 声明学生列表
    List<Student> students = new ArrayList<Student>();

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select * from t_student where department like ?";
    try {
        // 3. 创建预备语句对象
        PreparedStatement pstmt = conn.prepareStatement(strSQL);
        // 4. 设置占位符的值
        pstmt.setString(1, department + "%");
        // 5. 执行SQL，返回结果集
        ResultSet rs = pstmt.executeQuery();
        // 6. 遍历结果集
        while (rs.next()) {
            // 创建学生实体
            Student student = new Student();
            // 利用当前记录各字段值设置学生实体属性
            student.setId(rs.getString("id"));
            student.setName(rs.getString("name"));
            student.setSex(rs.getString("sex"));
            student.setAge(rs.getInt("age"));
            student.setDepartment(rs.getString("department"));
            student.setClassname(rs.getString("class"));
            student.setTelephone(rs.getString("telephone"));
            // 将实体添加到学生列表
            students.add(student);
        }
        // 7. 关闭结果集
        rs.close();
        // 8. 关闭预备语句对象
        pstmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回学生列表
    return students;
}


@Override
public List<Student> findAll() {
    // 声明学生列表
    List<Student> students = new ArrayList<Student>();

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select * from t_student";
    try {
        // 3. 创建语句对象
        Statement stmt = conn.createStatement();
        // 4. 执行SQL，返回结果集
        ResultSet rs = stmt.executeQuery(strSQL);
        // 5. 遍历结果集
        while (rs.next()) {
            // 创建学生实体
            Student student = new Student();
            // 利用当前记录各字段值设置学生实体属性
            student.setId(rs.getString("id"));
            student.setName(rs.getString("name"));
            student.setSex(rs.getString("sex"));
            student.setAge(rs.getInt("age"));
            student.setDepartment(rs.getString("department"));
            student.setClassname(rs.getString("class"));
            student.setTelephone(rs.getString("telephone"));
            // 将实体添加到学生列表
            students.add(student);
        }
        // 6. 关闭结果集
        rs.close();
        // 7. 关闭语句对象
        stmt.close();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回学生列表
    return students;
}

/**
 * 按性别统计学生人数
 *
 * @return 统计结果向量
 */
@Override
public Vector findRowsBySex() {
    // 定义行集向量
    Vector rows = new Vector();

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select sex as '性别', count(*) as '人数'"
            + " from t_student group by sex order by sex desc";
    try {
        // 3. 创建语句对象
        Statement stmt = conn.createStatement();
        // 4. 执行SQL，返回结果集
        ResultSet rs = stmt.executeQuery(strSQL);
        // 5. 遍历结果集
        while (rs.next()) {
            // 定义当前行向量
            Vector<String> currentRow = new Vector();
            // 利用当前记录字段值设置当前行向量的元素值
            currentRow.addElement(rs.getString("性别"));
            currentRow.addElement(rs.getInt("人数") + "");
            // 将当前行向量添加到行集向量
            rows.addElement(currentRow);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回行集向量
    return rows;
}


@Override
public Vector findRowsByClass() {
    // 定义行集向量
    Vector rows = new Vector();

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select class as '班级', count(*) as '人数'"
            + " from t_student group by class order by class desc";
    try {
        // 3. 创建语句对象
        Statement stmt = conn.createStatement();
        // 4. 执行SQL，返回结果集
        ResultSet rs = stmt.executeQuery(strSQL);
        // 5. 遍历结果集
        while (rs.next()) {
            // 定义当前行向量
            Vector<String> currentRow = new Vector();
            // 利用当前记录字段值设置当前行向量的元素值
            currentRow.addElement(rs.getString("班级"));
            currentRow.addElement(rs.getInt("人数") + "");
            // 将当前行向量添加到行集向量
            rows.addElement(currentRow);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回行集向量
    return rows;
}


@Override
public Vector findRowsByDepartment() {
    // 定义行集向量
    Vector rows = new Vector();

    // 1. 获取数据库连接对象
    Connection conn = ConnectionManager.getConnection();
    // 2. 定义SQL字符串
    String strSQL = "select department as '系部', count(*) as '人数'"
            + " from t_student group by department order by department desc";
    try {
        // 3. 创建语句对象
        Statement stmt = conn.createStatement();
        // 4. 执行SQL，返回结果集
        ResultSet rs = stmt.executeQuery(strSQL);
        // 5. 遍历结果集
        while (rs.next()) {
            // 定义当前行向量
            Vector<String> currentRow = new Vector();
            // 利用当前记录字段值设置当前行向量的元素值
            currentRow.addElement(rs.getString("系部"));
            currentRow.addElement(rs.getInt("人数") + "");
            // 将当前行向量添加到行集向量
            rows.addElement(currentRow);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭数据库连接
        ConnectionManager.closeConnection(conn);
    }

    // 返回行集向量
    return rows;
}

}

撰写textStudentDaoImpl测试类

出现了错误