[JDBC] Dao and related implementation classes

Oc jklrr90y 2020-11-08 12:56:54
jdbc dao related implementation classes


DAO

  1. DAO:Data Access Object Classes and interfaces for accessing data information , Including the data of CRUD(Create、Retrival、Update、Delete), It doesn't contain any business-related information . Sometimes called :BaseDAO
  2. effect : In order to realize the modularization of functions , More conducive to code maintenance and upgrade .

3. Specifically

  • BaseDAO: We use it BaseDAO As the parent class of the class we want to implement the business
  • CustomerDAO Interface : We can create interface definition specifications for whatever functions we want to implement , Mainly for customer Common operations of tables
  • CustomerDAOImpl: And then implement this interface , Carry out specific operation of adding, deleting, modifying and checking
     Insert picture description here

BaseDAO.java

package com.flora2.dao;
import com.flora.util.JDBCUtils;
import java.lang.reflect.Field;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
/**
* @author flora
* @create 2020-11-06 20:42
*/
public class BaseDAO {

// General addition, deletion and modification operations ( Think about the business )
public void update(Connection connection, String sql, Object ...args){

PreparedStatement ps = null;
try {

//1. precompile sql sentence , return PreparedStatement Example 
ps = connection.prepareStatement(sql);
//2. Fill in placeholders 
for (int i = 0; i < args.length; i++) {

ps.setObject(i+1,args[i]);
}
//3. perform 
ps.execute();
} catch (Exception e) {

e.printStackTrace();
} finally {

//4. Closure of resources 
JDBCUtils.closeResource(null,ps);
}
}
// General query operations , Used to return a record in a data table Think about the business 
public <T>T getInstance(Connection connection,Class<T> clazz, String sql,Object... args){

PreparedStatement ps = null;
ResultSet resultSet = null;
try {

ps = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {

ps.setObject(i+1,args[i]);
}
resultSet = ps.executeQuery();
// Get metadata of result set 
ResultSetMetaData rsmd = resultSet.getMetaData();
// adopt ResultSetMetaData Get the number of columns in the result set 
int columnCount = rsmd.getColumnCount();
if(resultSet.next()){

T t = clazz.newInstance();
// Process each column of a row of data in the result set 
for (int i = 0; i < columnCount; i++) {

// Get column values 
Object columValue = resultSet.getObject(i + 1);
// Get the column name of each column 
//String columnName = rsmd.getColumnName(i + 1);
String columnLabel = rsmd.getColumnLabel(i + 1);
// to t Object specified columnName attribute ,columValue By reflection 
Field field = clazz.getDeclaredField(columnLabel);
field.setAccessible(true);
field.set(t,columValue);
}
return t;
}
} catch (Exception e) {

e.printStackTrace();
} finally {

JDBCUtils.closeResource(null,ps,resultSet);
}
return null;
}
// General query operations , Used to return a collection of multiple pieces of data in a table Think about the business 
public <T> List<T> getForList(Connection connection, Class<T> clazz, String sql, Object... args){

PreparedStatement ps = null;
ResultSet resultSet = null;
try {

connection = JDBCUtils.getConnection();
ps = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {

ps.setObject(i+1,args[i]);
}
resultSet = ps.executeQuery();
// Get metadata of result set 
ResultSetMetaData rsmd = resultSet.getMetaData();
// adopt ResultSetMetaData Get the number of columns in the result set 
int columnCount = rsmd.getColumnCount();
// Create a collection object 
ArrayList<T> list = new ArrayList<T>();
while(resultSet.next()){

T t = clazz.newInstance();
// Process each column of a row of data in the result set ; to t Property assignment specified by the object 
for (int i = 0; i < columnCount; i++) {

// Get column values 
Object columValue = resultSet.getObject(i + 1);
// Get the column name of each column 
//String columnName = rsmd.getColumnName(i + 1);
String columnLabel = rsmd.getColumnLabel(i + 1);
// to t Object specified columnName attribute ,columValue By reflection 
Field field = clazz.getDeclaredField(columnLabel);
field.setAccessible(true);
field.set(t,columValue);
}
list.add(t);
}
return list;
} catch (Exception e) {

e.printStackTrace();
} finally {

JDBCUtils.closeResource(null,ps,resultSet);
}
return null;
}
// A general method for querying special values 
public <E>E getValue(Connection connection,String sql, Object...args){

PreparedStatement ps = null;
ResultSet rs = null;
try {

ps = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {

ps.setObject(i+1,args[i]);
}
rs = ps.executeQuery();
if(rs.next()){

return (E)rs.getObject(1);
}
} catch (SQLException throwables) {

throwables.printStackTrace();
} finally {

JDBCUtils.closeResource(null,ps,rs);
}
return null;
}
}

CustomerDAO.java

Interface Define specification

package com.flora2.dao;
import com.flora.bean.Customer;
import java.sql.Connection;
import java.sql.Date;
import java.util.List;
/**
* This interface is used to specify for customer Common operations of tables
* @author flora
* @create 2020-11-06 20:57
*/
public interface CustomerDAO {

// take customer Object added to the database 
void insert(Connection connection, Customer customer);
// For the specified id, Delete a record in the table 
void deleteById(Connection connection,int id);
// For in memory customer object , To modify the record specified in the data table 
void update(Connection connection,Customer customer);
// For the specified id Query the corresponding Customer object 
Customer getCustomerById(Connection connection, int id);
// A collection of all records in a query table 
List<Customer> getAll(Connection connection);
// Returns the number of entries of data in the data table 
Long getCount(Connection connection);
Date getMaxBirth(Connection connection);
}

CustomerDAOImpl.java

package com.flora2.dao;
import com.flora.bean.Customer;
import java.sql.Connection;
import java.sql.Date;
import java.util.List;
/**
* @author flora
* @create 2020-11-06 21:09
*/
public class CustomerDAOImpl extends BaseDAO implements CustomerDAO{

@Override
public void insert(Connection connection, Customer customer) {

String sql = "insert into customers(name,email,birth)values(?,?,?)";
update(connection,sql,customer.getName(),customer.getEmail(),customer.getBirth());
}
@Override
public void deleteById(Connection connection, int id) {

String sql = "delete from customers where id=?";
update(connection,sql,id);
}
@Override
public void update(Connection connection, Customer customer) {

String sql = "update customers set name=?,email=?,birth=? where id=?";
update(connection,sql,customer.getName(),customer.getEmail(),customer.getBirth(),customer.getId());
}
@Override
public Customer getCustomerById(Connection connection, int id) {

String sql = "select id,name,email,birth from customers where id=?";
Customer customer = getInstance(connection, Customer.class,sql, id);
return customer;
}
@Override
public List<Customer> getAll(Connection connection) {

String sql = "select id,name,email,birth from customers";
List<Customer> list = getForList(connection, Customer.class, sql);
return list;
}
@Override
public Long getCount(Connection connection) {

String sql = "select count(*) from customers";
return getValue(connection,sql);
}
@Override
public Date getMaxBirth(Connection connection) {

String sql = "select max(birth) from customers";
return getValue(connection,sql);
}
}

test CustomerDAOImplTest

Not finished Lazy to write

package com.flora2.dao.junit;
import com.flora.bean.Customer;
import com.flora.util.JDBCUtils;
import com.flora2.dao.CustomerDAOImpl;
import java.sql.Connection;
import java.sql.Date;
import static org.junit.jupiter.api.Assertions.*;
/**
* @author flora
* @create 2020-11-06 21:31
*/
class CustomerDAOImplTest {

CustomerDAOImpl dao = new CustomerDAOImpl();
@org.junit.jupiter.api.Test
void insert() {

Connection connection = null;
try {

connection = JDBCUtils.getConnection();
Customer customer = new Customer(1," Yu Xiaofei ","xiaofei@1265.com",new Date(47842892892829L));
dao.insert(connection,customer);
System.out.println(" Add success ");
} catch (Exception e) {

e.printStackTrace();
} finally {

JDBCUtils.closeResource(connection,null);
}
}
@org.junit.jupiter.api.Test
void deleteById() {

}
@org.junit.jupiter.api.Test
void update() {

}
@org.junit.jupiter.api.Test
void getCustomerById() {

}
@org.junit.jupiter.api.Test
void getAll() {

}
@org.junit.jupiter.api.Test
void getCount() {

}
@org.junit.jupiter.api.Test
void getMaxBirth() {

}
}

The upgrade version is to put Customer.class Get rid of , I didn't write it specifically , Again jdbc Of the 45 Set

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本文为[Oc jklrr90y]所创,转载请带上原文链接,感谢

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