课堂练习（mysql--java）

DAO实现类

<span style="color: #000000;">@Override
    </span><span style="color: #0000ff;">public</span> List<Student> selectStudents() <span style="color: #0000ff;">throws</span><span style="color: #000000;"> Exception {
        List</span><Student> list=<span style="color: #0000ff;">new</span> ArrayList<Student><span style="color: #000000;">();
        String sql</span>="select * from Student,grade where Student.gradeid=grade.gradeid"<span style="color: #000000;">;
        ResultSet exe </span>=<span style="color: #000000;"> executeQuery(sql);
        </span><span style="color: #0000ff;">if</span> (exe!=<span style="color: #0000ff;">null</span><span style="color: #000000;">) {
            </span><span style="color: #0000ff;">while</span><span style="color: #000000;"> (exe.next()) {
                Student stu</span>=<span style="color: #0000ff;">new</span><span style="color: #000000;"> Student();
                grade grade</span>=<span style="color: #0000ff;">new</span><span style="color: #000000;"> grade();
                stu.setStudentname(exe.getString(</span>"studentname"<span style="color: #000000;">));
                stu.setSex(exe.getInt(</span>"sex"<span style="color: #000000;">));
                grade.setGradename(exe.getString(</span>"gradename"<span style="color: #000000;">));
                stu.setGrade(grade);
                list.add(stu);
            }
        }
        closs();
        </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> list;
    }</span>

entity

<span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> stduentNo;
    </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String loginpwd;
    </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String studentname;
    </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> sex;
    </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> gradeid;
    </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String phone;
    </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String address;
    </span><span style="color: #0000ff;">private</span> grade grade=<span style="color: #0000ff;">new</span> grade();

2.查询S1年级下的学生记

DAO实现类

<span style="color: #000000;">@Override
    </span><span style="color: #0000ff;">public</span> grade selegrade(String gradename) <span style="color: #0000ff;">throws</span><span style="color: #000000;"> Exception {
        grade grade</span>=<span style="color: #0000ff;">new</span><span style="color: #000000;"> com.myschool.entity.grade();
        String sql</span>="select * from Student,grade where Student.gradeid=grade.gradeid and gradename=?"<span style="color: #000000;">;
        ResultSet rs </span>=<span style="color: #000000;"> executeQuery(sql, gradename);
        </span><span style="color: #0000ff;">if</span> (rs!=<span style="color: #0000ff;">null</span><span style="color: #000000;">) {
            </span><span style="color: #0000ff;">while</span><span style="color: #000000;"> (rs.next()) {
                grade.setGradename(rs.getString(</span>"gradename"<span style="color: #000000;">));
                Student stu</span>=<span style="color: #0000ff;">new</span><span style="color: #000000;"> Student();
                stu.setStudentname(rs.getString(</span>"studentname"<span style="color: #000000;">));
                grade.getListStudents().add(stu);
            }
        }
        closs();
        </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> grade;
    }</span>

entity

<span style="color: #0000ff;">private</span> <span style="color: #0000ff;">int</span><span style="color: #000000;"> gradeid;
    </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String gradename;
    </span><span style="color: #0000ff;">public</span> List<Student> listStudents=<span style="color: #0000ff;">new</span> ArrayList<Student>();

课堂练习（mysql--java）

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