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上一篇博客寫到如何連接數(shù)據(jù)庫和增刪查改，但是每一次操作都需要寫一個(gè)類，體現(xiàn)不到類的封裝性，這篇博客講詳細(xì)介紹到如何封裝類，并快速實(shí)現(xiàn)增刪查改。

前提準(zhǔn)備：

1.建包 

com.tao.entity 用于盛放實(shí)體類

com.tao.dao 用于接口的實(shí)現(xiàn)類

com.tao.test 用于測(cè)試類

2.建表

通過mysql，在school數(shù)據(jù)庫下建立person表，

字段有id（int），name（varchar），pass（varchar），birthday（date）

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BaseDao是一個(gè)基類，里面寫好了一個(gè)連接數(shù)據(jù)庫的方法connect（）和一個(gè) 關(guān)閉資源的方法closeAll（）；其他接口的實(shí)現(xiàn)類繼承這個(gè)類，并調(diào)用他的方法即可。

BaseDao.java

package com.tao.dao;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.Statement;

public class BaseDao {

protected Connection conn = null;

protected Statement stmt = null;

protected ResultSet rs = null;

protected String url = "jdbc:mysql://localhost:3306/school?characterEncoding=utf-8";

protected String name = "root";

protected String password = "root";

protected PreparedStatement pstmt=null;

public void connect(){

try {

Class.forName("com.mysql.jdbc.Driver");

conn = DriverManager.getConnection(url, "root", "root");

stmt = conn.createStatement();

} catch(Exception e) {

e.printStackTrace();

}

}

public void closeAll(){

try {

if (rs != null) {

rs.close();

}

if (stmt != null) {

stmt.close();

}

if (conn != null) {

conn.close();

}

if(pstmt!=null){

pstmt.close();

}

}catch(Exception e) {

}

}

}

插入代碼片

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接下來，我們可以創(chuàng)建一個(gè)person類

Person.java

package com.tao.entity;

import java.util.Date;

public class Person {

private int id;

private String name;

private String pass;

private String birthday;

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getPass() {

return pass;

}

public void setPass(String pass) {

this.pass = pass;

}

public String getBirthday() {

return birthday;

}

public void setBirthday(String birthday) {

this.birthday = birthday;

}

@Override

public String toString() {

return "Person [id=" + id + ", name=" + name + ", pass=" + pass

+ ", birthday=" + birthday + "]";

}

}

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然后寫PersonDao類，這個(gè)類繼承BaseDao，實(shí)現(xiàn)增刪查改的方法

package com.tao.dao;

import com.tao.entity.Person;

public class PersonDao extends BaseDao {

/*

* 登錄

*/

public Person dologin(String name, String pass) {

Person s = null;

try {

super.connect();

// String sql = "select * from person where name='" + name

// + "' and pass='" + pass + "'";

// rs = stmt.executeQuery(sql);

String sql="select * from person where name=? and pass=?";

pstmt=conn.prepareStatement(sql);

pstmt.setString(1, name);

pstmt.setString(2, pass);

rs=pstmt.executeQuery();

while (rs.next()) {

s = new Person();

s.setId(rs.getInt(1));

s.setName(rs.getString(2));

s.setPass(rs.getString(3));

s.setBirthday(rs.getString(4));

}

} catch (Exception e) {

// TODO: handle exception

}

return s;

}

/*

* 刪除

*/

public int delete(int id){

int row=0;

try {

super.connect();

String sql="delete from person where id="+id;

row=stmt.executeUpdate(sql);

} catch (Exception e) {

// TODO: handle exception

}

return row;

}

/*

* 插入

*/

public int insert(Person p){

int row=0;

try {

super.connect();

// String sql="insert into person values("+p.getId()+",'"+p.getName()+"','"+p.getPass()+"','"+p.getBirthday()+"')";

// row=stmt.executeUpdate(sql);

String sql="insert into person(name,pass,birthday) values(?,?,?)";

pstmt=conn.prepareStatement(sql);

pstmt.setString(1, p.getName());

pstmt.setString(2, p.getPass());

pstmt.setString(3, p.getBirthday());

row=pstmt.executeUpdate();

} catch (Exception e) {

e.printStackTrace();

}

return row;

}

/*

* 查詢一個(gè)人

*/

public Person get(int id) {

Person s = null;

try {

super.connect();

String sql = "select * from person where id="+id;

rs = stmt.executeQuery(sql);

while (rs.next()) {

s = new Person();

s.setId(rs.getInt(1));

s.setName(rs.getString(2));

s.setPass(rs.getString(3));

s.setBirthday(rs.getString(4));

}

} catch (Exception e) {

// TODO: handle exception

}

return s;

}

/*

* 修改

*/

public int update(Person p){

int row=0;

try {

super.connect();

String sql="update person set name='"+p.getName()+"',pass='"+p.getPass()+"', birthday='"+p.getBirthday()+"' where id="+p.getId();

row=stmt.executeUpdate(sql);

} catch (Exception e) {

e.printStackTrace();

}

return row;

}

}

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最后寫測(cè)試類，測(cè)試結(jié)果

TestP.java

package com.tao.test;

import com.tao.dao.PersonDao;

import com.tao.entity.Person;

public class TestP {

public static void main(String[] args) {

/*

* 登錄測(cè)試

*/

PersonDao pdao = new PersonDao();

Person p1 = pdao.dologin("jack", "1' or'1'='1");

if (p1 == null) {

System.out.println("登錄失敗");

} else {

System.out.println("登陸成功");

System.out.println(p1);

}

/*

* 刪除測(cè)試

*/

int row = pdao.delete(5);

if (row > 0) {

System.out.println("del success..");

} else {

System.out.println("del failed");

}

/*

* 插入測(cè)試

*/

/*Person p2 = new Person();

p2.setName("xiaoliu");

p2.setPass("xiaoliu");

p2.setBirthday("2018-8-18");

int r=pdao.insert(p2);

if (r > 0) {

System.out.println("insert success..");

} else {

System.out.println("insert failed");

}*/

/*

* 查詢一個(gè)獲取學(xué)生并修改姓名

* 

*/

Person p3 = new Person();

p3 = pdao.get(3);

p3.setName("tom1");

int rr = pdao.update(p3);

if (rr > 0) {

System.out.println("update success..");

} else {

System.out.println("update failed");

}

}

}

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