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Teach you JDBC hand in hand -- structure separation

2022-07-03 00:39:00 【Gorit】

JDBC Learning notes —— Structural separation

Preparation
One 、 Realize your second JDBC Program

1.1 Basic structure of the project
1.2 BaseDao Structural separation

1.2.1 establish jdbc.properties file
1.2.2 establish ConfigProperty.java file
1.2.3 establish Contranct.java file

1.3 Dao Layer separation

1.3.1 UserDao Interface implementation
1.3.2 UserDaoImpl class ,UserDao Method implementation of
Looking back

Preparation

Basic configuration see me

One 、 Realize your second JDBC Program

1.1 Basic structure of the project

Hands teach you how to JDBC —— Structural separation _mysql

Explanation of three packages ：

dao Package created under UserDao class , Realize the most basic method of adding, deleting, modifying and checking
entity Package created under User class , Add basic User Basic information of as well as getter and setter Method
util It's a bag , Use BaseDao Class to JDBC Perform packaging work

1.2 BaseDao Structural separation

1.2.1 establish jdbc.properties file

stay util In bag , We will BaseDao The part of the registration driver in is further subdivided , Store the four element file of registration drive in In a file , It's packaged twice (jdbc.properties), And add the following

       
        #mysql
        
jdbc.driver=com.mysql.jdbc.Driver
        
jdbc.url=jdbc:mysql://localhost:3306/bank?userUnicode=true&characterEncoding=utf8
        
jdbc.username=root
        
jdbc.password=root
       
       
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1.2.2 establish ConfigProperty.java file

Used below Properties class , Then use this class to read jdbc.properties Properties file

       
        package cn.jdbc.util;
        

        
import java.io.IOException;
        
import java.io.InputStream;
        
import java.util.Properties;
        

        

        
public class ConfigProperty {
        
  //Properties（Java.util.Properties）, Mainly used to read Java Configuration file for 
        
  Properties properties = null;
        
  private static ConfigProperty instance = null;
        

        
  private ConfigProperty() {
        
    properties = new Properties();//  Create a property file object 
        
    //  Get the input stream -- The reflex mechanism 
        
    InputStream is = ConfigProperty.class.getClassLoader()
        
        .getResourceAsStream("jdbc.properties");
        
    try {
        
      properties.load(is);
        
    } catch (IOException e) {
        
      e.printStackTrace();
        
    }
        
  }
        

        
  public static ConfigProperty getInstance() {
        
    if (instance == null) {
        
      instance = new ConfigProperty();
        
    }
        
    return instance;
        
  }
        

        
  public String getValueByKey(String key) {//  according to key, Find value 
        
    return properties.getProperty(key);
        
  }
        
}
       
       
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1.2.3 establish Contranct.java file

Create a Contranct Interface . And then

       
        package cn.jdbc.util;
        

        
public interface Contranct {
        
    public static final String DRIVER=ConfigProperty.getInstance().getValueByKey("jdbc.driver");
        
    public static final String URL=ConfigProperty.getInstance().getValueByKey("jdbc.url");
        
    public static final String NAME=ConfigProperty.getInstance().getValueByKey("jdbc.username");
        
    public static final String PWD=ConfigProperty.getInstance().getValueByKey("jdbc.password");
        
}
       
       
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Why do you do this ？

Because it did , Only modify the configuration in the future jdbc.properties Can be configured , The code can basically be changed
Then add the corresponding database driver

1.3 Dao Layer separation

take UserDao Separate into the following two parts

UserDao Class to UserDaoT class
Add a new one UserDao Interface
Add a new one UserDaoImpl class , Inherit BaseDao class as well as UserDao Interface , Final realization Data addition, deletion, modification and query

1.3.1 UserDao Interface implementation

       
        package cn.jdbc.dao;
        

        
import cn.jdbc.entity.User;
        

        
public interface UserDao {
        
  User selectUserByuserNameAndPwd(String userName, String pwd);
        

        
}
       
       
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1.3.2 UserDaoImpl class ,UserDao Method implementation of

       
        package cn.jdbc.dao.Impl;
        

        
import java.sql.SQLException;
        

        
import cn.jdbc.dao.UserDao;
        
import cn.jdbc.entity.User;
        
import cn.jdbc.util.BaseDao;
        

        

        
public class UserDaoImpl extends BaseDao implements UserDao{
        

        
  @Override
        
  public User selectUserByuserNameAndPwd(String userName, String pwd) {
        
    // TODO Auto-generated method stub
        
    User user = null;
        
    String sql = "SELECT *FROM USER WHERE username=? AND pwd=?";
        
    Object[] params = { userName, pwd };
        
    rs = this.executeQuery(sql, params);
        
    try {
        
      if (rs.next()) {
        
        user = new User(rs.getString("username"), rs.getString("pwd"),
        
            rs.getString("status"), rs.getString("qq"),
        
            rs.getTimestamp("registerTime"));
        
      }
        
    } catch (SQLException e) {
        
      e.printStackTrace();
        
    }
        
    return user;
        
  }
        

        
}
       
       
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