Multi-table query under the three-tier structure, the entity class writing

One relationship

　　All student information query, information is displayed in grades Grade name

　　A, DAO layer structures:

　　　　1. entity classes:

　　　　　　Student categories:

package com.myschool.entity;

import java.io.Serializable;
import java.util.Date;

public class Student implements Serializable {
	
	private static final long serialVersionUID = 6439763802252472361L;
	
	//定义实体属性
	private int studentNo;
	private String longinPwd;
	private String studentName;
	private int sex;
	private grade grade;//把年级对象作为属性
	private String phone;
	private String address;
	private Date bornDate;
	private String email;
	private String identityCard;
	
        //封装
	public int getStudentNo() {
		return studentNo; 
	}
	public void setStudentNo(int studentNo) {
		this.studentNo = studentNo;
	}
	public String getLonginPwd() {
		return longinPwd;
	}
	public void setLonginPwd(String longinPwd) {
		this.longinPwd = longinPwd;
	}
	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 grade getGrade() {
		return grade;
	}
	public void setGrade(grade grades) {
		this.grade = grades;
	}
	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 Date getBornDate() {
		return bornDate;
	}
	public void setBornDate(Date 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) {
		this.identityCard = identityCard;
	}
	
       //有参构造
	public Student(int studentNo, String longinPwd, String studentName,
			int sex, grade gradeID, String phone, String address, Date bornDate,
			String email, String identityCard) {
		this.studentNo = studentNo;
		this.longinPwd = longinPwd;
		this.studentName = studentName;
		this.sex = sex;
		this.gradeID = gradeID;
		this.phone = phone;
		this.address = address;
		this.bornDate = bornDate;
		this.email = email;
		= identityCard this.identityCard; 
	} // constructor with no arguments 
	public Student () { 
	}

	
		

　　　　　Grade categories:

package com.myschool.entity;

public class grade {
    private int gradeid;
    private String gradeName;
    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;
    }
    public grade(int gradeid, String gradeName) {
        super();
        this.gradeid = gradeid;
        this.gradeName = gradeName;
    }
    public grade() {
        super();
        
    }
    
}

　　　　Corresponding to a year as a student, but not in the table relates to the student grades names, grades encapsulated objects directly to the student attributes

　　　　2.Daobase: database access classes connection

package com.myschool.dao;

import java.beans.Statement;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class baseDao {

    // 创建连接参数
    private final static String DRIVER = "com.mysql.jdbc.Driver";
    private final static String URL = "jdbc:mysql:///myschool";
    private final static String USER_NAME = "root";
    private final static String PASSWORD = "123";

    Connection con = null;
    PreparedStatement prestatement = null;
    ResultSet rs = null;

    // 获取连接
    private Connection getConnection() {
        try {
            Class.forName(DRIVER);
            if (con == null) {
                con = DriverManager.getConnection(URL, USER_NAME, PASSWORD);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        returnCON; 
    } 

    // CRUD 
    public  int the executeUpdate (String SQL, ... Object obj) throws Exception {
         // Get connecting 
        the getConnection (); 

        // Get the object prepareStatement 
        prestatement = con.prepareStatement (SQL); 

        // cycle add parameters 
        for ( int I =. 1; I <= obj.length; I ++ ) { 
            prestatement.setObject (I, obj [I -. 1 ]); 
        } 
        // execute SQL statements 
        int COUNT = prestatement.executeUpdate ();
         return COUNT; 

    } 

    //Check 
    public the ResultSet the executeQuery (String SQL, ... Object obj) throws Exception {
         // Get connecting 
        the getConnection (); 

        // Get the object prepareStatement 
        prestatement = con.prepareStatement (SQL); 

        // cycle parameters added 
        for ( int I =. 1 ; I ++; <= obj.length I ) { 
            prestatement.setObject (I, obj [I -. 1 ]); 
        } 
        // execute SQL statements 
        RS = prestatement.executeQuery (); 

        return RS; 

    } 
    
    // resource recovery 
    public  void closeResouse ()throws Exception
    {
        if (rs!=null) {
            rs.close();
        }
        if (prestatement!=null) {
            prestatement.close();
        }
        if (con!=null) {
            con.close();
        }
        
    }
 
}

 

　　　　3.DAO Interface:

Package Penalty for com.myschool.dao; 

Import java.util.List; 

Import com.myschool.entity.Student; 

public  interface IStudentDao { 

    / * 
     * Query all student records, grades name 
     * / 
    public List <Student> Search () throws Exception; 

    
}

 

　　　　　4.DAO interface categories:

package com.mychool.dao.impl;

import java.sql.ResultSet;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;

import com.myschool.dao.IStudentDao;
import com.myschool.dao.baseDao;
import com.myschool.entity.Student;
import com.myschool.entity.grade;

public class IStudentDaoImpl extends baseDao implements IStudentDao {

    
    @Override
    public List<Student> Search() throws Exception {
        //创建student对象泛型集合
        List <Student> = stus new new the ArrayList <Student> (); String SQL
        
        = "studentName the Select, from Student GradeName, WHERE Grade.gradeid = Student.gradeid Grade" ; 

        // definition of the object receiving resultSet basedao query methods found out data 
        rSet ResultSet = executeQuery (SQL); 
        
        IF (! rSet = null ) {
             the while (rSet.next ()) { 
                Student STU = new new Student (); 
                Grade Grade = new new Grade (); // create an object grades
 //                 STU. setAddress (rSet.getString ( "address")
 );//                stu.setEmail(rSet.getString("email"));
//                stu.setIdentityCard(rSet.getString("identityCard"));
//                stu.setLonginPwd(rSet.getString("longinPwd"));
//                stu.setPhone(rSet.getString("phone"));
//                stu.setSex(rSet.getInt("sex"));
                grade.setGradeName(rSet.getString("gradeName"));//给年级对象赋值
                stu.setStudentName(rSet.getString("studentName"));//给学生对象赋值
                stu.setGradeID(grade);
//                stu.setStudentNo(rSet.getInt("StudentNo"));
//                = New new sdFormat the SimpleDateFormat the SimpleDateFormat ( "the MM-dd-YYYY");
 //                 stu.setBornDate (sdFormat.parse (rSet.getString ( "bornDate"))); 
                stus.add (STU); // add objects to the student the object set 
            } 
            
        } 
　　　　// release resources recycling 
        closeResouse () ;
         return stus; 
    } 

    
} 
to clean clear and simple, not part of the attribute value query

　　Two, service layer:

　　There is no logic what, I'll just quote the dao method again, not to explain

　　　　1.service Interface:

package com.myschool.service;

import java.util.List;

import com.myschool.entity.Student;

public interface IService {
    
    public List<Student> Search() throws Exception;
}

　　　　2.service interface categories:

package com.mychool.service.Impl;

import java.util.List;

import com.mychool.dao.impl.IStudentDaoImpl;
import com.myschool.dao.IStudentDao;
import com.myschool.entity.Student;
import com.myschool.service.IService;

public class IServiceImpl implements IService{

    IStudentDao isd=new IStudentDaoImpl();
    @Override
    public List<Student> Search() throws Exception {
        return isd.Search();
    }
    
}

　　Three, UI layer:

　　　　

package com.myschool.ui;

import java.util.List;

import com.mychool.service.Impl.IServiceImpl;
import com.myschool.entity.Student;
import com.myschool.service.IService;

public class test {    
    public static void main(String[] args) throws Exception {
　　　　　//创建service接口实现类的对象
        IService isv=new  IServiceImpl();
        List<Student> lsList=isv.Search();

        for (Student student : lsList) {
            System.out.println(student.getStudentName()+"\t"+student.getGradeID().getGradeName());
        }
    }
}

Many relationship

　　The main difference here is the implementation class package and dao wording:

　　Since a plurality of grades corresponding to students, the student package a collection of generic objects in the class grade.

　　　　DAO implementation class writing: