JDBC代码实现
数据库结构：
表：
t_course：
t_course_teacher：
t_student：
t_student_course：
t_teacher:
代码结构：
Dao包下的代码；
package dao;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.math.BigDecimal;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import util.ConnectionUtil;
public class Dao<T> {
private Class<T> clazz;
@SuppressWarnings("unchecked")
public Dao() {
Type type = this.getClass().getGenericSuperclass();
if (type instanceof ParameterizedType) {
ParameterizedType parameterizedType = (ParameterizedType) type;
Type[] types = parameterizedType.getActualTypeArguments();
if (type != null && types.length > 0) {
if (types[0] instanceof Class) {
clazz = (Class<T>) types[0];
}
}
}
}
public T querOne(String sql, Object... args) {
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
T entity = null;
try {
connection = ConnectionUtil.getConnection();
preparedStatement=connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
resultSet = preparedStatement.executeQuery();
if (resultSet != null) {
ResultSetMetaData resultSetMetaData = resultSet.getMetaData(); // 获取元数据
int colCounts = resultSetMetaData.getColumnCount();// 获取列数
if (resultSet.next()) {
entity = clazz.newInstance();
for (int i = 0; i < colCounts; i++) {
String colname = resultSetMetaData
.getColumnLabel(i + 1);
System.out.println(colname);
Object colValue = resultSet.getObject(i + 1);
Field field = clazz.getDeclaredField(colname);
field.setAccessible(true);
if (colValue instanceof BigDecimal) {
double value = ((BigDecimal) colValue)
.doubleValue();
System.out.println(value);
field.set(entity, value);
} else {
field.set(entity, colValue);
}
field.setAccessible(false);
}
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
ConnectionUtil
.release(resultSet, preparedStatement, connection);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return entity;
}
public List<T> querMany(String sql, Object... args) {
List<T> entitys=new ArrayList<T>();
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
T entity = null;
try {
connection = ConnectionUtil.getConnection();
preparedStatement=connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
resultSet = preparedStatement.executeQuery();
if (resultSet != null) {
ResultSetMetaData resultSetMetaData = resultSet.getMetaData(); // 获取结果集元数据，获取查询集中有几列，各个列的名称是什么
int colCounts = resultSetMetaData.getColumnCount();// 获取列数
while (resultSet.next()) { //使内部游标推进到下一条记录
entity = clazz.newInstance();
for (int i = 0; i < colCounts; i++) {
String colname = resultSetMetaData
.getColumnLabel(i + 1);
System.out.println(colname);
Object colValue = resultSet.getObject(i + 1);
Field field = clazz.getDeclaredField(colname);
field.setAccessible(true);
if (colValue instanceof BigDecimal) {
double value = ((BigDecimal) colValue)
.doubleValue();
System.out.println(value);
field.set(entity, value);
} else {
field.set(entity, colValue);
}
field.setAccessible(false);
}
entitys.add(entity);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
ConnectionUtil
.release(resultSet, preparedStatement, connection);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return entitys;
}
public static void update(String sql, Object... args) throws Exception {
Connection conn = null;
PreparedStatement preparedStatement = null;
try {
conn = ConnectionUtil.getConnection();
preparedStatement = conn.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
preparedStatement.executeUpdate();
} finally {
try {
ConnectionUtil.release(null, preparedStatement, conn);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
package dao;
import entity.Course;
public class CourseDao extends Dao<Course>{
}
package dao;
import entity.Student;
public class StudentDao extends Dao<Student> {
}
entity下的代码：
package entity;
/**
* @author mabin
*Data 2020-9-6
* PackageName entity
*ProjectName JDBC00
*FileName Course.java
*TODO TODO
*/
public class Course {
private String c_no;
private String c_name;
private String c_type;
private double c_credit;
private int c_time;
public Course() {
// TODO Auto-generated constructor stub
}
public Course(String c_no,String c_name,String c_type,double c_credit,int c_time) {
this.c_no=c_no;
this.c_name=c_name;
this.c_type=c_type;
this.c_credit=c_credit;
this.c_time=c_time;
}
public String getC_no() {
return c_no;
}
public void setC_no(String c_no) {
this.c_no = c_no;
}
public String getC_name() {
return c_name;
}
public void setC_name(String c_name) {
this.c_name = c_name;
}
public String getC_type() {
return c_type;
}
public void setC_type(String c_type) {
this.c_type = c_type;
}
public double getC_credit() {
return c_credit;
}
public void setC_credit(double c_credit) {
this.c_credit = c_credit;
}
public int getC_time() {
return c_time;
}
public void setC_time(int c_time) {
this.c_time = c_time;
}
@Override
public String toString() {
return "Course [c_no=" + c_no + ", c_name=" + c_name + ", c_type=" + c_type
+ ", c_credit=" + c_credit + ", c_time=" + c_time + "]";
}
}
package entity;
import java.util.Date;
public class Student {
private String s_no;
private String s_name;
private String s_grade;
private Date s_birdth;
private String s_majer;
private String s_class;
private String s_phone;
private String s_addr;
public Student(){
}
public Student(String s_no, String s_name, String s_grade, Date s_birdth,
String majer, String s_class, String s_phone, String s_addr) {
this.s_no = s_no;
this.s_name = s_name;
this.s_grade = s_grade;
this.s_birdth = s_birdth;
this.s_majer = majer;
this.s_class = s_class;
this.s_phone = s_phone;
this.s_addr = s_addr;
}
public String getS_no() {
return s_no;
}
public void setS_no(String s_no) {
this.s_no = s_no;
}
public String getS_name() {
return s_name;
}
public void setS_name(String s_name) {
this.s_name = s_name;
}
public String getS_grade() {
return s_grade;
}
public void setS_grade(String s_grade) {
this.s_grade = s_grade;
}
public Date getS_birdth() {
return s_birdth;
}
public void setS_birdth(Date s_birdth) {
this.s_birdth = s_birdth;
}
public String getMajer() {
return s_majer;
}
public void setMajer(String majer) {
this.s_majer = majer;
}
public String getS_class() {
return s_class;
}
public void setS_class(String s_class) {
this.s_class = s_class;
}
public String getS_phone() {
return s_phone;
}
public void setS_phone(String s_phone) {
this.s_phone = s_phone;
}
public String getS_addr() {
return s_addr;
}
public void setS_addr(String s_addr) {
this.s_addr = s_addr;
}
@Override
public String toString() {
return "Student [s_no=" + s_no + ", s_name=" + s_name + ", s_grade="
+ s_grade + ", s_birdth=" + s_birdth + ", majer=" + s_majer
+ ", s_class=" + s_class + ", s_phone=" + s_phone + ", s_addr="
+ s_addr + "]";
}
}
util包下的代码：
package util;
import java.io.BufferedInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class ConnectionUtil {
public static Connection getConnection() throws Exception{
BufferedInputStream bis=new BufferedInputStream(ConnectionUtil.class.getClassLoader().getResourceAsStream("conn.properties"));
Connection conn=null;
Properties properties=new Properties();
properties.load(bis);
String driverClassName=properties.getProperty("driverclass");
String url=properties.getProperty("url");
String username=properties.getProperty("username");
String password=properties.getProperty("password");
Class.forName(driverClassName);
conn=DriverManager.getConnection(url,username,password);
System.out.println("连接成功！！");
return conn;
}
public static void release(ResultSet resultSet,Statement statement,Connection conn)throws SQLException{
if(statement!=null){statement.close();}
if(conn!=null){conn.close();}
if(resultSet!=null){resultSet.close();}
System.out.println("连接已关闭");
}
}
test包下的代码：
package test;
import java.util.List;
import org.junit.Test;
import dao.CourseDao;
import dao.StudentDao;
import entity.Course;
import entity.Student;
public class DBTest {
public static void main(String[] args) {
}
@Test
public void courseTest(){
String sql="select c_no,c_name,c_type from t_coures where c_no=?";
CourseDao courseDao=new CourseDao();
Course course1=courseDao.querOne(sql, "220141402");
System.out.println(course1);
String sql2="select c_no,c_name,c_type,c_credit,c_time from t_coures where c_no=?";
CourseDao courseDao2=new CourseDao();
Course course2=courseDao2.querOne(sql2, "220141402");
System.out.println(course2);
}
@Test
public void studentTest(){
// String sql="select s_no,s_name,s_grade, s_birdth,s_majer,s_class,s_phone,s_addr from t_student where s_no=?";
// StudentDao studentDao=new StudentDao();
// Student student1=studentDao.querOne(sql, "2020081208");
// System.out.println(student1);
String sql2="select s_no,s_name,s_grade, s_birdth,s_majer,s_class,s_phone,s_addr from t_student ";
StudentDao studentDao2=new StudentDao();
List<Student> student2=studentDao2.querMany(sql2);
System.out.println(student2);
}
}
config文件夹下的文件：
mysql驱动：
本文来自博客园，作者：极地阳光-ing，转载请注明原文链接：https://www.cnblogs.com/Polar-sunshine/p/13626137.html
