易筋SpringBoot 2.1 | 第六篇：JdbcTemplate訪問MySQL
阿新 • • 發佈：2019-01-03
寫作時間：2019-01-03
Spring Boot: 2.1 ,JDK: 1.8, IDE: IntelliJ IDEA, MySQL 8.0.13
說明
資料需要持久化儲存，無論是客戶端的SQLLITE，還是服務端的MySQL。這裡記錄最原始的訪問資料庫方式，JdbcTemplate訪問MySQL. Spring 提供了一個模板類JdbcTemplate，能夠容易跟資料庫和資料庫連線JDBC(Java DataBase Connectivity)打交道。 絕大多數的JDBC程式碼在寫業務程式碼之前需要很多準備工作：獲取資料庫資源，連線管理，異常處理，常規錯誤校驗. JdbcTemplate幫你處理上面的所有問題， 讓開發者專注於業務.
MySQL資料庫
-
首先需要到MySQL的官網下載社群版的安裝檔案。筆者下載的是最新版本8.0.13.
-
接下來：下載 > 安裝 > 設定root密碼(mysql8.0以上密碼策略限制必須要大小寫加數字特殊符號)
安裝完成以後，安裝路徑在/usr/local，筆者的MySQL路徑為：/usr/local/mysql-8.0.13-macos10.14-x86_64。 -
在命令列輸入mysql命令：
$ mysql
zsh: command not found: mysql
- 發現找不到命令，需要先設定環境變數，筆者的命令列環境為myzsh，設定如下：
$ cd $home
$ vim .zshrc
- 在最下面加上環境變數配置
# Mysql
export MYSQL_HOME="/usr/local/mysql-8.0.13-macos10.14-x86_64"
export PATH=$MYSQL_HOME/bin:$PATH
- 儲存esc >
:wq, 重新載入配置檔案
$ source .zshrc
- 連線資料庫：
$ mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; - 新建資料庫和使用者(注意：
--後面是註釋)
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
- 顯示資料庫：
mysql> show databases
-> ;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| db_example |
+--------------------+
5 rows in set (0.00 sec)
- 選擇資料庫
mysql> use mysql;
Database changed
- 顯示資料庫中的表
mysql> show tables;
+---------------------------+
| Tables_in_mysql |
+---------------------------+
| columns_priv |
| component |
...
MySQL客戶端
在命令列裡面寫sql不方便，可以下載客戶端MySQL Workbench 8.0.13，查詢例子如下，執行快捷鍵cmd+enter
忘記root密碼也可以修改，建議儲存好密碼。
工程建立
參照教程【SpringBoot 2.1 | 第一篇：構建第一個SpringBoot工程】新建一個Spring Boot專案，名字叫demojdbctemplate, 在目錄src/main/java/resources 下找到配置檔案application.properties，重新命名為application.yml。
配置檔案
pom.xml 依賴配置新增：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.13</version>
</dependency>
MySQL連線的配置mysql-connector-java資訊來自官網 »
資料庫連線資訊配置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
程式碼實現
- 新建實體類
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;
}
}
- 完善啟動類
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()));
}
}
實現功能解說：
1)注入jdbcTemplate物件
2)建立表customers
3)插入資料
4)查詢滿足條件firstName='Josh'的記錄
- 執行工程, 控制檯列印資訊如下：
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']
總結
恭喜你！實現了JdbcTemplate訪問MySQL。 企業專案一般會用Mybatis或者JPA操作資料庫，所以這裡只要會用JdbcTemplate就好。
程式碼下載：
https://github.com/zgpeace/Spring-Boot2.1/tree/master/demojdbctemplate
參考：
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