sdent类：
package com.myschool.entity; public class student{ private int studentno; private String loginpwd; private String studentname; private int sex; private int gradeid; private String phone; private String address; private String borndate; private String email; private String IdentityCard; grade grade=new grade(); public grade getGrade() { return grade; } public void setGrade(grade grade) { this.grade = grade; } public int getStudentno() { return studentno; } public void setStudentno(int studentno) { this.studentno = studentno; } public String getLoginpwd() { return loginpwd; } public void setLoginpwd(String loginpwd) { this.loginpwd = loginpwd; } public String getStudentname() { return studentname; } public void setStudentname(String studentname) { this.studentname = studentname; } public int getSex() { return sex; } public void setSex(int sex) { this.sex = sex; } public int getGradeid() { return gradeid; } public void setGradeid(int gradeid) { this.gradeid = gradeid; } public String getPhone() { return phone; } public void setPhone(String phone) { this.phone = phone; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public String getBorndate() { return borndate; } public void setBorndate(String borndate) { this.borndate = borndate; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public String getIdentityCard() { return IdentityCard; } public void setIdentityCard(String identityCard) { IdentityCard = identityCard; } //带参构造 public student(int studentno, String loginpwd, String studentname, int sex, int gradeid, String phone, String address, String borndate, String email, String identityCard) { super(); this.studentno = studentno; this.loginpwd = loginpwd; this.studentname = studentname; this.sex = sex; this.gradeid = gradeid; this.phone = phone; this.address = address; this.borndate = borndate; this.email = email; IdentityCard = identityCard; } //无参构造 public student(){ } }
grade类：
package com.myschool.entity; import java.util.List; public class grade { private int gradeid; private String gradename; public List<student> list; public List<student> getList() { return list; } public void setList(List<student> list) { this.list = list; } public int getGradeid() { return gradeid; } public void setGradeid(int gradeid) { this.gradeid = gradeid; } public String getGradename() { return gradename; } public void setGradename(String gradename) { this.gradename = gradename; } //带参构造 public grade(int gradeid, String gradename) { super(); this.gradeid = gradeid; this.gradename = gradename; } //无参构造 public grade(){ } } BaseDao接口： package com.myschool.daos; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; public class BaseDao { private static final String STRING="com.mysql.jdbc.Driver"; private static final String URL="jdbc:mysql:///myschool"; private static final String U_STRING="root"; private static final String PASSWORD=""; Connection con=null; PreparedStatement Statement; ResultSet executeQuery ; public Connection getdConnection() throws Exception { Class.forName(STRING); //con.isClosed:判断是否是关闭的 if (con==null||con.isClosed()) { con = DriverManager.getConnection(URL, U_STRING,PASSWORD); } return con; } //Object ...objects这种参数定义是在不确定方法参数的情况下的一种多态表现形式。 //即这个方法可以传递多个参数，这个参数的个数是不确定的。这样你在方法体中需要相应的做些处理。 //因为Object是基类，所以使用Object ...objects这样的参数形式，允许一切继承自Object的对象作为参数。 //这种方法在实际中应该还是比较少用的。 public int getDao(String string,Object...objects) throws Exception { getdConnection(); Statement = con.prepareStatement(string); for (int i = 1; i <=objects.length; i++) { Statement.setObject(i,objects[i-1]); } int execute = Statement.executeUpdate(); return execute; } public ResultSet getDaos(String string,Object...objects) throws Exception { getdConnection(); Statement = con.prepareStatement(string); for (int i = 1; i <=objects.length; i++) { Statement.setObject(i,objects[i-1]); } executeQuery = Statement.executeQuery(); return executeQuery; } public void close() throws Exception { if (executeQuery!=null) { executeQuery.close(); } if (Statement!=null) { Statement.close(); } if (con!=null) { con.close(); } } } 接口： package com.myschool.daos; import java.util.List; import com.myschool.entity.grade; import com.myschool.entity.student; public interface studentdao { public List<student> getstudent() throws Exception; public grade getgrade(String gradeid) throws Exception; } 实现类： package com.myschool.dao.impl; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import com.myschool.daos.BaseDao; import com.myschool.daos.studentdao; import com.myschool.entity.grade; import com.myschool.entity.student; public class studnetdaoimpl extends BaseDao implements studentdao{ private ResultSet rs=null; @Override public grade getgrade(String gradename) throws Exception { List<student> list1=new ArrayList<student>(); String sql="select s.*,g.GradeName from student as s,grade as g where s.GradeId=g.GradeId and g.gradename=?"; Object[] obj={gradename}; rs=executeQuery(sql, obj); grade grade=null; if (rs!=null) { while(rs.next()){ grade=new grade(); student student=new student(); student.setStudentno(rs.getInt("studentno")); student.setStudentname(rs.getString("studentname")); list1.add(student); grade.setGradename(rs.getString("gradename")); } grade.setList(list1); } return grade; } @Override public List<student> getstudent() throws Exception { List<student> list=new ArrayList<student>(); String sql="select * from student as s,grade as g where s.GradeId=g.GradeId"; rs = executeQuery(sql); if (rs!=null) { while(rs.next()){ student stu=new student(); grade grade=new grade(); stu.setStudentno(rs.getInt("studentno")); stu.setStudentname(rs.getString("studentname")); grade.setGradename(rs.getString("gradename")); stu.setGrade(grade); list.add(stu); } } return list; } } main方法： package ui; import java.util.List; import com.myschool.dao.impl.studnetdaoimpl; import com.myschool.daos.studentdao; import com.myschool.entity.grade; import com.myschool.entity.student; public class ui { static studentdao dao=new studnetdaoimpl(); public static void getstudent() throws Exception{ List<student> list=dao.getstudent(); for (student student : list) { System.out.println(student.getStudentno()+"\t"+student.getStudentname()+"\t"+student.getGrade().getGradename()); } } public static void main(String[] args) throws Exception { getstudent(); grade grade=dao.getgrade("S1"); for (student stu : grade.getList()) { System.out.println(stu.getStudentno()+"\t"+stu.getStudentname()+"\t"+grade.getGradename()); } } }转载于:https://www.cnblogs.com/lowerma/p/10945018.html
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