SpringBoot - 05. 数据访问之JDBC（源码分析+代码下载）

时间 2020-04-24

标签 springboot 数据访问 jdbc 源码分析代码下载栏目 Spring 繁體版

原文原文链接

1、JDBC是什么？

JDBC API 属于Java APIJDBC用于如下几种功能：链接到数据库、执行SQL语句html

2、Spring Boot中如何使用JDBC

2.1 建立 Spring Boot Project 时引入 JDBC API 依赖和 MySQL Driver依赖，以及Spring Web依赖（测试时用到）

能够在POM中找到引入的JDBC依赖和mysql依赖： JDBC 依赖：java

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>

MySql 驱动依赖：mysql

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <scope>runtime</scope>
</dependency>

2.2 配置数据库链接

新增配置文件：src/main/resources/application.ymlgit

spring:
  datasource:
    username: root
    password: root
    url: jdbc:mysql://localhost:3306/study-spring-boot?serverTimezone=UTC&useUnicode=true&zeroDateTimeBehavior=convertToNull&autoReconnect=true&characterEncoding=utf-8
    driverClassName: com.mysql.cj.jdbc.Driver

注意：com.mysq.jdbc.Driver 被废弃了，须要使用com.mysql.cj.jdbc.Drivergithub

2.3 查看使用的数据源和数据库链接

package com.jackson0714.springboot;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;


@SpringBootTest
class Springboot05DataJdbcApplicationTests {

	@Autowired
	DataSource dataSource; //自动配置数据源，使用yml配置

	@Test
	void contextLoads() throws SQLException {
		System.out.println("数据源：" + dataSource.getClass());

		Connection connection = dataSource.getConnection();
		System.out.println("数据库链接：" + connection);
		connection.close();
	}

}

默认数据源：class com.zaxxer.hikari.HikariDataSourceweb

数据库链接：HikariProxyConnection@1335157064 wrapping com.mysql.cj.jdbc.ConnectionImpl@7ff8a9dcspring

3、自动配置原理

自动配置文件路径：org.springframework.boot.autoconfigure.jdbcsql

DataSourceConfiguration用来自动导入数据源（根据各类判断）shell

/**
	 * Tomcat Pool DataSource configuration.
	 */
	@Configuration(proxyBeanMethods = false)
	@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)
	@ConditionalOnMissingBean(DataSource.class)
	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.tomcat.jdbc.pool.DataSource",
			matchIfMissing = true)
	static class Tomcat {

		@Bean
		@ConfigurationProperties(prefix = "spring.datasource.tomcat")

3.1 自动选择数据源

若是导入了org.apache.tomcat.jdbc.pool.DataSource数据源，而且配置的spring.datasource.type配置的是org.apache.tomcat.jdbc.pool.DataSource，或没配置type也使用tomcat数据源数据库

3.2 HikariDataSource数据源也相似这样判断。

3.3 默认使用tomcat数据源

3.4 默认支持如下数据源

org.apache.tomcat.jdbc.pool、HikariDataSource、org.apache.commons.dbcp2

3.5 支持自定义数据源

使用DataSourceBuilder建立数据源，利用反射建立响应type的数据源，而且绑定相关属性

/**
	 * Generic DataSource configuration.
	 */
	@Configuration(proxyBeanMethods = false)
	@ConditionalOnMissingBean(DataSource.class)
	@ConditionalOnProperty(name = "spring.datasource.type")
	static class Generic {

		@Bean
		DataSource dataSource(DataSourceProperties properties) {
          //使用DataSourceBuilder建立数据源，利用反射建立响应type的数据源，而且绑定相关属性
			return properties.initializeDataSourceBuilder().build();
		}

	}

3.6 DataSourceInitializerInvoker 运行脚本

/**
 * Bean to handle {@link DataSource} initialization by running {@literal schema-*.sql} on
 * {@link InitializingBean#afterPropertiesSet()} and {@literal data-*.sql} SQL scripts on
 * a {@link DataSourceSchemaCreatedEvent}.
 *
 * @author Stephane Nicoll
 * @see DataSourceAutoConfiguration
 */
class DataSourceInitializerInvoker implements ApplicationListener<DataSourceSchemaCreatedEvent>, InitializingBean {

createSchema() 建立表 （文件名规则 schema-*.sql）
initSchema() 执行数据脚本 （文件名规则 data-*.sql）

getScripts() 来获取须要执行的脚本

private List<Resource> getScripts(String propertyName, List<String> resources, String fallback) {
  if (resources != null) {
    return getResources(propertyName, resources, true);
  }
  String platform = this.properties.getPlatform();
  List<String> fallbackResources = new ArrayList<>();
  fallbackResources.add("classpath*:" + fallback + "-" + platform + ".sql");
  fallbackResources.add("classpath*:" + fallback + ".sql");
  return getResources(propertyName, fallbackResources, false);
}

fallback = "schema", platform="all",会自动执行根目录下：schema-all.sql 或schema.sql 文件
fallback = "data", platform="all",会自动执行根目录下：data-all.sql 或data.sql 文件

isEnabled() 方法判断是否开启了自动执行脚本

有三种模式：NEVER，EMBEDDED（默认），Always

疑问：用EMBEDDED模式返回false，开关关闭，不执行脚本，这是为啥呢？

用Always模式则每次启动spring boot重复执行脚本（建立表脚本都是先判断有没有表，有则删除后重建）

private boolean isEnabled() {
  DataSourceInitializationMode mode = this.properties.getInitializationMode();
  if (mode == DataSourceInitializationMode.NEVER) {
    return false;
  }
  if (mode == DataSourceInitializationMode.EMBEDDED && !isEmbedded()) {
    return false;
  }
  return true;
}

3.7 经过配置文件指定须要执行脚本

schema:
  - classpath:department.sql

建立出的 department 表

4、JdbcTemplate

JdbcTemplateAutoConfiguration.java 文件自动注入了JdbcTemplate。（JdbcTemplate用来操做数据库）

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ DataSource.class, JdbcTemplate.class })
@ConditionalOnSingleCandidate(DataSource.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
@EnableConfigurationProperties(JdbcProperties.class)
@Import({ JdbcTemplateConfiguration.class, NamedParameterJdbcTemplateConfiguration.class })
public class JdbcTemplateAutoConfiguration {

}

咱们用Swagger的方式来测试

5、配置Swagger用来测试

5.1 pom.xml文件添加swagger依赖

<!-- swagger -->
<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger2</artifactId>
  <version>2.9.2</version>
</dependency>
<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger-ui</artifactId>
  <version>2.9.2</version>
</dependency>

5.2 添加SwaggerConfig.java文件

package com.jackson0714.springboot.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

@Configuration
@EnableSwagger2
public class SwaggerConfig {

    @Bean
    public Docket createRestApi(){
        return new Docket(DocumentationType.SWAGGER_2).apiInfo(apiInfo())
                .select()
                .apis(RequestHandlerSelectors.any())
                .paths(PathSelectors.any()).build();
    }

    private ApiInfo apiInfo(){
        return new ApiInfoBuilder()
                .title("玩转Spring Boot 接口文档")
                .description("This is a restful api document of Spring Boot.")
                .version("1.0")
                .build();
    }

}

5.3 访问Swagger文档

http://localhost:8081/swagger-ui.html

6、测试

6.1 新增部门

@ApiOperation(value = "1.新增部门")
@ApiImplicitParams({
  @ApiImplicitParam(name = "name", value = "部门名称")
})
@PostMapping("/create")
public int createDepartment(@RequestParam String name) {
  String sql = String.format("insert into department(departmentName) value('%s')", name);
  int result = jdbcTemplate.update(sql);
  return result;
}

表记录

6.2 查询全部部门

@ApiOperation(value = "2.查询全部部门")
@GetMapping("/getAllDepartment")
public List<Map<String, Object>> getAllDepartment() {
  List<Map<String, Object>> list = jdbcTemplate.queryForList("select * from department");
  return list;
}

6.3 根据id查询某个部门

@ApiOperation(value = "3.根据id查询某个部门")
@ApiImplicitParams({
  @ApiImplicitParam(name = "id", value = "须要查询的部门id")
})
@GetMapping("/{id}")
public Map<String, Object> getDepartmentById(@PathVariable Long id) {
  String sql = "select * from department where id = " + id;
  List<Map<String, Object>> list = jdbcTemplate.queryForList(sql);
  return list.get(0);
}

6.4 根据id更新部门名称

@ApiOperation(value = "根据id更新部门名称")
@ApiImplicitParams({
  @ApiImplicitParam(name = "id", value = "须要更新的部门id"),
  @ApiImplicitParam(name = "name", value = "须要更新的部门名称")
})
@PostMapping("/update")
public int updateDepartmentById(@RequestParam Long id, @RequestParam String name) {
  String sql = String.format("update department set departmentName = '%s' where id = %d", name, id);
  int result = jdbcTemplate.update(sql);
  return result;
}

6.5 根据id删除部门

@ApiOperation(value = "根据id删除部门")
@ApiImplicitParams({
  @ApiImplicitParam(name = "id", value = "须要删除的部门id")
})
@PostMapping("/delete")
public int deleteDepartment(@RequestParam Long id) {
  String sql = String.format("delete from department where id = %d", id);
  int result = jdbcTemplate.update(sql);
  return result;
}

7、报错和解决方案：

7.1 问题1

java.sql.SQLException:null, message from server: "Host 'Siri' is not allowed to connect to this MySQL server" 解决方案：执行命令：

use mysql;
select host from user;
update user set host = '%' where user = 'root'

执行结果：

Query OK, 1 row affected

以下图所示：

7.2 问题2

Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value '�й��׼ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support. 解决方案：配置spring.datasource.url 时，增长参数：serverTimezone=UTC

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