# 第四章:Spring的数据库开发
JDBC: Java Database Connector
JdbcTemplate方法
## 一、execute()
#### (1)mysql创建数据库spring
```mysql
create database spring;
```
#### (2)导包
五个核心包:commons-logging spring-core spring-beans spring-context spring-expression
其他两个包:spring-jdbc mysql-connector-java
```java
org.springframework
spring-context
4.3.6.RELEASE
mysql
mysql-connector-java
8.0.28
org.springframework
spring-jdbc
4.3.6.RELEASE
```
#### (3)创建配置文件a.xml
```java
```
#### (4)测试execute()方法
```java
package com.gzh;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.jdbc.core.JdbcTemplate;
public class JdbcTest {
public static void main(String[] args) {
ApplicationContext applicationContext =new ClassPathXmlApplicationContext("a.xml");
JdbcTemplate jdbcTemplate = (JdbcTemplate) applicationContext.getBean("jdbcTemplate");
String sql="create table account(id int primary key auto_increment,username varchar (50),balance double)";
jdbcTemplate.execute(sql);
}
}
```
运行结果如下:数据库中已经成功创建表account
![image-20220329195454770](https://yovinchen-1308133012.cos.ap-beijing.myqcloud.com/image-20220329195454770.png)
## 二、update():增删改
实体类对象 转换 表中记录
### 实体类:
(1)和表对应,一张表对应一个实体类
(2)实体类中的成员变量 表中字段一一对应(数据类型 名称)
(3)实体类中的作用就是和表进行数据传输
SSM项目分三层:dao层 服务层 控制层,此代码为了简便,只创建dao层
dao层:
接口:接口中所有方法就是系统的功能。 面向接口编程
实现类:声明了一个JdbcTemplate类对象
### 步骤:
#### (1)创建实体类
```java
package com.gzh.domain;
public class Account {
private int id;
private String username;
private double balance;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public double getBalance() {
return balance;
}
public void setBalance(double balance) {
this.balance = balance;
}
@Override
public String toString() {
return "Account{" +
"id=" + id +
", username='" + username + '\'' +
", balance=" + balance +
'}';
}
}
```
#### (2)创建接口
```java
package com.gzh.dao;
import com.gzh.domain.Account;
public interface AccountDao {
//增加记录
int addAccount(Account account);
//删除根据用户ID删除账户
int deleteById(int id);
//更新记录
int updateAccount(Account account);
}
```
#### (3)实现接口
```java
package com.gzh.dao;
import com.gzh.domain.Account;
import org.springframework.jdbc.core.JdbcTemplate;
public class AccountDaoImpl implements AccountDao {
private JdbcTemplate jdbcTemplate;
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
//增加记录
@Override
public int addAccount(Account account) {
String sql = "insert into account values(?,?,?)";
int update = jdbcTemplate.update(sql, account.getId(), account.getUsername(), account.getBalance());
return update;
}
//删除根据用户ID删除账户
@Override
public int deleteById(int id) {
String sql = "delete from account where id=?";
int update = jdbcTemplate.update(sql, id);
return update;
}
//更新记录
@Override
public int updateAccount(Account account) {
String sql = "update account set username=?,balance=? where id=?";
int update = jdbcTemplate.update(sql, account.getUsername(), account.getBalance(), account.getId());
return update;
}
}
```
#### (4)写配置文件
```java
```
#### (5)测试Test方法
```java
package com.gzh;
import com.gzh.dao.AccountDao;
import com.gzh.domain.Account;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class JdbcTest {
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("a.xml");
AccountDao accountDao = (AccountDao) applicationContext.getBean("accountDao");
@Test
//增加记录
public void addAccountTets() {
Account account = new Account();
account.setId(1);
account.setUsername("zhangsan");
account.setBalance(1000);
accountDao.addAccount(account);
}
@Test
//删除根据用户ID删除账户
public void deleteByIdTest() {
accountDao.deleteById(1);
}
@Test
//更新记录
public void updateAccountTest() {
Account account = new Account();
account.setUsername("zhangsan");
account.setBalance(3000);
account.setId(1);
accountDao.updateAccount(account);
}
}
```
#### 运行截图:
1.创建两个数据
![image-20220331221520933](https://yovinchen-1308133012.cos.ap-beijing.myqcloud.com/image-20220331221520933.png)
2.测试删除数据
![image-20220331221604934](https://yovinchen-1308133012.cos.ap-beijing.myqcloud.com/image-20220331221604934.png)
3.更新数据
![image-20220331221704292](https://yovinchen-1308133012.cos.ap-beijing.myqcloud.com/image-20220331221704292.png)
### 补充:
#### 1.Object
当方法形参个数不确定的时候,可以使用Object...,代表的是多个多种类型的参数
#### 2.基本数据类型 包装类
int Integer
double Double
```
int a = 5;
Integer b = a; //装箱
int c = b; //拆箱
```
#### 3.单元测试
可以直接运行一个非main方法的方法 @Test
```java
public class AccountDao{
@Test
public void cat(){
System.out.println("a");
}
@Test
public void cat(){
System.out.println("b");
}
}
```
## 三、query():查
表中的记录 转换 实体类对象
### 步骤:
#### (1)创建实体类
同上
#### (2)创建接口
```java
//查询 根据id进行查询 单条记录
Account findAccountById(int id);
//查所有记录
List findAllAccounts();
```
#### (3)实现接口
```java
//查询 根据id进行查询 单条记录
@Override
public Account findAccountById(int id) {
String sql = "select * from account where id =?";
RowMapper rowMapper = new BeanPropertyRowMapper<>(Account.class);
Account account = jdbcTemplate.queryForObject(sql, rowMapper, id);
return account;
}
//查所有记录
@Override
public List findAllAccounts() {
String sql = "select * from account";
RowMapper rowMapper = new BeanPropertyRowMapper(Account.class);
List account = jdbcTemplate.query(sql, rowMapper);
return account;
}
```
#### (4)写配置文件
同上
#### (5)测试Test方法
```java
@Test
//查询 根据id进行查询 单条记录
public void findAccountByIdTest() {
Account accountById = accountDao.findAccountById(1);
System.out.println(accountById);
}
@Test
//查所有记录
public void findAllAccoundsTest() {
List accounts = accountDao.findAllAccounts();
for (Account i : accounts) {
System.out.println(i);
}
}
```
#### 运行截图:
1.单个查询
![image-20220331223326855](https://yovinchen-1308133012.cos.ap-beijing.myqcloud.com/image-20220331223326855.png)
2.多项查询
![image-20220331223422159](https://yovinchen-1308133012.cos.ap-beijing.myqcloud.com/image-20220331223422159.png)