易筋SpringBoot 2.1 | 第六篇：JdbcTemplate访问MySQL
写作时间：2019-01-03
Spring Boot: 2.1 ,JDK: 1.8, IDE: IntelliJ IDEA, MySQL 8.0.13
说明
数据需要持久化保存，无论是客户端的SQLLITE，还是服务端的MySQL。这里记录最原始的访问数据库方式，JdbcTemplate访问MySQL. Spring 提供了一个模板类JdbcTemplate，能够容易跟数据库和数据库连接JDBC(Java DataBase Connectivity)打交道。 绝大多数的JDBC代码在写业务代码之前需要很多准备工作：获取数据库资源，连接管理，异常处理，常规错误校验. JdbcTemplate帮你处理上面的所有问题， 让开发者专注于业务.
MySQL数据库
-
首先需要到MySQL的官网下载社区版的安装文件。笔者下载的是最新版本8.0.13.
-
接下来：下载 > 安装 > 设置root密码(mysql8.0以上密码策略限制必须要大小写加数字特殊符号)
安装完成以后，安装路径在/usr/local，笔者的MySQL路径为：/usr/local/mysql-8.0.13-macos10.14-x86_64。 -
在命令行输入mysql命令：
$ mysql
zsh: command not found: mysql
- 发现找不到命令，需要先设置环境变量，笔者的命令行环境为myzsh，设置如下：
$ cd $home
$ vim .zshrc
- 在最下面加上环境变量配置
# Mysql
export MYSQL_HOME="/usr/local/mysql-8.0.13-macos10.14-x86_64"
export PATH=$MYSQL_HOME/bin:$PATH
- 保存esc >
:wq, 重新加载配置文件
$ source .zshrc
- 连接数据库：
$ mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 24
Server version: 8.0.13 MySQL Community Server - GPL
- 新建数据库和用户(注意：
--后面是注释)
mysql> create database db_example; -- Create the new database
mysql> create user 'springuser'@'%' identified by 'ThePassword'; -- Creates the user
mysql> grant all on db_example.* to 'springuser'@'%'; -- Gives all the privileges to the new user on the newly created database
- 显示数据库：
mysql> show databases
-> ;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| db_example |
+--------------------+
5 rows in set (0.00 sec)
- 选择数据库
mysql> use mysql;
Database changed
- 显示数据库中的表
mysql> show tables;
+---------------------------+
| Tables_in_mysql |
+---------------------------+
| columns_priv |
| component |
...
MySQL客户端
在命令行里面写sql不方便，可以下载客户端MySQL Workbench 8.0.13，查询例子如下，执行快捷键cmd+enter
忘记root密码也可以修改，建议保存好密码。
工程建立
参照教程【SpringBoot 2.1 | 第一篇：构建第一个SpringBoot工程】新建一个Spring Boot项目，名字叫demojdbctemplate, 在目录src/main/java/resources 下找到配置文件application.properties，重命名为application.yml。
配置文件
pom.xml 依赖配置添加：
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-jdbcartifactId>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.13version>
dependency>
MySQL连接的配置mysql-connector-java信息来自官网 »
- 8.0.13 链接
- 所有版本链接
如果没有配置mysql-connector-java，或者配置的版本不对，会报错Unable to create initial connections of pool ，
数据库连接信息配置src/main/resources/application.yml：
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/db_example
username: springuser
password: ThePassword
可能会遇到的错误：Warning about SSL connection when connecting to MySQL database
解决方法, 修改url的配置如下：url: jdbc:mysql://localhost:3306/db_example?autoReconnect=true&useSSL=false
上面配置会禁止SSL并抑制SSL错误.
参考：stackoverflow
代码实现
- 新建实体类
com.zgpeace.demojdbctemplate.bean.Customer
package com.zgpeace.demojdbctemplate.bean;
public class Customer {
private long id;
private String firstName, lastName;
public Customer(long id, String firstName, String lastName) {
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
}
@Override
public String toString() {
return String.format(
"Customer[id=%d, firstName='%s', lastName='%s']",
id, firstName, lastName);
}
// getters & setters omitted for brevity
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
}
- 完善启动类
com.zgpeace.demojdbctemplate.DemojdbctemplateApplication
package com.zgpeace.demojdbctemplate;
import com.zgpeace.demojdbctemplate.bean.Customer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.jdbc.core.JdbcTemplate;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
@SpringBootApplication
public class DemojdbctemplateApplication implements CommandLineRunner {
private static final Logger log = LoggerFactory.getLogger(DemojdbctemplateApplication.class);
@Autowired
JdbcTemplate jdbcTemplate;
public static void main(String[] args) {
SpringApplication.run(DemojdbctemplateApplication.class, args);
}
@Override
public void run(String... args) throws Exception {
log.info("Creating tables");
jdbcTemplate.execute("DROP TABLE IF EXISTS customers");
jdbcTemplate.execute("CREATE TABLE customers(" +
"id SERIAL, first_name VARCHAR(255), last_name VARCHAR(255))");
// Split up the array of whole names into an array of first/last names
List<Object[]> splitUpNames = Arrays.asList("John Woo", "Jeff Dean", "Josh Bloch", "Josh Long").stream()
.map(name -> name.split(" "))
.collect(Collectors.toList());
// Use a Java 8 stream to print out each tuple of the list
splitUpNames.forEach(name -> log.info(String.format("Inserting customer record for %s %s", name[0], name[1])));
// Uses JdbcTemplate's batchUpdate operation to bulk load data
jdbcTemplate.batchUpdate("INSERT INTO customers(first_name, last_name) VALUES (?,?)", splitUpNames);
log.info("Querying for customer records where first_name = 'Josh':");
jdbcTemplate.query("SELECT id, first_name, last_name FROM customers WHERE first_name = ?", new Object[] { "Josh"},
(rs, rowNum) -> new Customer(rs.getLong("id"), rs.getString("first_name"),
rs.getString("last_name"))).forEach(customer -> log.info(customer.toString()));
}
}
实现功能解说：
1)注入jdbcTemplate对象
2)创建表customers
3)插入数据
4)查询满足条件firstName='Josh'的记录
- 运行工程, 控制台打印信息如下：
2019-01-03 10:51:35.301 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Creating tables
2019-01-03 10:51:35.303 INFO 23276 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2019-01-03 10:51:35.626 INFO 23276 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
2019-01-03 10:51:35.723 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Inserting customer record for John Woo
2019-01-03 10:51:35.723 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Inserting customer record for Jeff Dean
2019-01-03 10:51:35.723 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Inserting customer record for Josh Bloch
2019-01-03 10:51:35.723 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Inserting customer record for Josh Long
2019-01-03 10:51:35.743 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Querying for customer records where first_name = 'Josh':
2019-01-03 10:51:35.755 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Customer[id=3, firstName='Josh', lastName='Bloch']
2019-01-03 10:51:35.755 INFO 23276 --- [ main] c.z.d.DemojdbctemplateApplication : Customer[id=4, firstName='Josh', lastName='Long']
总结
恭喜你！实现了JdbcTemplate访问MySQL。 企业项目一般会用Mybatis或者JPA操作数据库，所以这里只要会用JdbcTemplate就好。
代码下载：
https://github.com/zgpeace/Spring-Boot2.1/tree/master/db/demojdbctemplate
参考：
https://spring.io/guides/gs/relational-data-access/
https://spring.io/guides/gs/accessing-data-mysql/
https://blog.csdn.net/forezp/article/details/70477821
https://www.jianshu.com/p/a8e4068a7a8a