【MYSQL】Java的JDBC编程（idea连接数据库）

1. 配置

（1）新建一个项目

（2）Build System 那里选择Maven,下一步Create

（3）配置pom.xml文件
首先查看自己的MYSQL版本：进入MySQL命令窗口

我的MYSQL版本是8.0版本的.

下一步，去Maven官网：Maven
点击搜索框，输入Java，回车

点击下图这个：

找到对应版本点击进去，比如我的是8.0.28，那我就点即8.0.x最新版的8.0.33。

下拉，点击Maven，复制里边的代码。

回到我们刚创建的Java项目，在pom文件中
先写以下代码：

<dependencies>  </dependencies>

再把刚才从Maven中复制的代码放到上面代码的中间。（通常情况会报错，这是正常的）：

（4）setting文件

新建一个setting文件，文件后缀是.xml，然后在文件中填入下面的代码，记住文件路径，记得保存。

<?xml version="1.0" encoding="UTF-8"?><!--
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specific language governing permissions and limitations
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--><!--| This is the configuration file for Maven. It can be specified at two levels:||  1. User Level. This settings.xml file provides configuration for a single user,|                 and is normally provided in ${user.home}/.m2/settings.xml.||                 NOTE: This location can be overridden with the CLI option:||                 -s /path/to/user/settings.xml||  2. Global Level. This settings.xml file provides configuration for all Maven|                 users on a machine (assuming they're all using the same Maven|                 installation). It's normally provided in|                 ${maven.conf}/settings.xml.||                 NOTE: This location can be overridden with the CLI option:||                 -gs /path/to/global/settings.xml|| The sections in this sample file are intended to give you a running start at| getting the most out of your Maven installation. Where appropriate, the default| values (values used when the setting is not specified) are provided.||-->
<settings xmlns="http://maven.apache.org/SETTINGS/1.2.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.2.0 https://maven.apache.org/xsd/settings-1.2.0.xsd"><!-- localRepository| The path to the local repository maven will use to store artifacts.|| Default: ${user.home}/.m2/repository<localRepository>/path/to/local/repo</localRepository>--><!-- interactiveMode| This will determine whether maven prompts you when it needs input. If set to false,| maven will use a sensible default value, perhaps based on some other setting, for| the parameter in question.|| Default: true<interactiveMode>true</interactiveMode>--><!-- offline| Determines whether maven should attempt to connect to the network when executing a build.| This will have an effect on artifact downloads, artifact deployment, and others.|| Default: false<offline>false</offline>--><!-- pluginGroups| This is a list of additional group identifiers that will be searched when resolving plugins by their prefix, i.e.| when invoking a command line like "mvn prefix:goal". Maven will automatically add the group identifiers| "org.apache.maven.plugins" and "org.codehaus.mojo" if these are not already contained in the list.|--><pluginGroups><!-- pluginGroup| Specifies a further group identifier to use for plugin lookup.<pluginGroup>com.your.plugins</pluginGroup>--></pluginGroups><!-- proxies| This is a list of proxies which can be used on this machine to connect to the network.| Unless otherwise specified (by system property or command-line switch), the first proxy| specification in this list marked as active will be used.|--><proxies><!-- proxy| Specification for one proxy, to be used in connecting to the network.|<proxy><id>optional</id><active>true</active><protocol>http</protocol><username>proxyuser</username><password>proxypass</password><host>proxy.host.net</host><port>80</port><nonProxyHosts>local.net|some.host.com</nonProxyHosts></proxy>--></proxies><!-- servers| This is a list of authentication profiles, keyed by the server-id used within the system.| Authentication profiles can be used whenever maven must make a connection to a remote server.|--><servers><!-- server| Specifies the authentication information to use when connecting to a particular server, identified by| a unique name within the system (referred to by the 'id' attribute below).|| NOTE: You should either specify username/password OR privateKey/passphrase, since these pairings are|       used together.|<server><id>deploymentRepo</id><username>repouser</username><password>repopwd</password></server>--><!-- Another sample, using keys to authenticate.<server><id>siteServer</id><privateKey>/path/to/private/key</privateKey><passphrase>optional; leave empty if not used.</passphrase></server>--></servers><!-- mirrors| This is a list of mirrors to be used in downloading artifacts from remote repositories.|| It works like this: a POM may declare a repository to use in resolving certain artifacts.| However, this repository may have problems with heavy traffic at times, so people have mirrored| it to several places.|| That repository definition will have a unique id, so we can create a mirror reference for that| repository, to be used as an alternate download site. The mirror site will be the preferred| server for that repository.|--><mirrors><!-- mirror| Specifies a repository mirror site to use instead of a given repository. The repository that| this mirror serves has an ID that matches the mirrorOf element of this mirror. IDs are used| for inheritance and direct lookup purposes, and must be unique across the set of mirrors.|<mirror><id>mirrorId</id><mirrorOf>repositoryId</mirrorOf><name>Human Readable Name for this Mirror.</name><url>http://my.repository.com/repo/path</url></mirror><mirror><id>nexus-aliyun</id><mirrorOf>*</mirrorOf><name>Nexus aliyun</name><url>http://maven.aliyun.com/nexus/content/groups/public</url></mirror> <mirror><id>maven-default-http-blocker</id><mirrorOf>external:http:*</mirrorOf><name>Pseudo repository to mirror external repositories initially using HTTP.</name><url>http://0.0.0.0/</url><blocked>true</blocked></mirror>--><mirror><id>aliyun-public</id><mirrorOf>*</mirrorOf><name>aliyun public</name><url>https://maven.aliyun.com/repository/public</url></mirror><mirror><id>aliyun-central</id><mirrorOf>*</mirrorOf><name>aliyun central</name><url>https://maven.aliyun.com/repository/central</url></mirror><mirror><id>aliyun-spring</id><mirrorOf>*</mirrorOf><name>aliyun spring</name><url>https://maven.aliyun.com/repository/spring</url></mirror></mirrors><!-- profiles| This is a list of profiles which can be activated in a variety of ways, and which can modify| the build process. Profiles provided in the settings.xml are intended to provide local machine-| specific paths and repository locations which allow the build to work in the local environment.|| For example, if you have an integration testing plugin - like cactus - that needs to know where| your Tomcat instance is installed, you can provide a variable here such that the variable is| dereferenced during the build process to configure the cactus plugin.|| As noted above, profiles can be activated in a variety of ways. One way - the activeProfiles| section of this document (settings.xml) - will be discussed later. Another way essentially| relies on the detection of a system property, either matching a particular value for the property,| or merely testing its existence. Profiles can also be activated by JDK version prefix, where a| value of '1.4' might activate a profile when the build is executed on a JDK version of '1.4.2_07'.| Finally, the list of active profiles can be specified directly from the command line.|| NOTE: For profiles defined in the settings.xml, you are restricted to specifying only artifact|       repositories, plugin repositories, and free-form properties to be used as configuration|       variables for plugins in the POM.||--><profiles><!-- profile| Specifies a set of introductions to the build process, to be activated using one or more of the| mechanisms described above. For inheritance purposes, and to activate profiles via <activatedProfiles/>| or the command line, profiles have to have an ID that is unique.|| An encouraged best practice for profile identification is to use a consistent naming convention| for profiles, such as 'env-dev', 'env-test', 'env-production', 'user-jdcasey', 'user-brett', etc.| This will make it more intuitive to understand what the set of introduced profiles is attempting| to accomplish, particularly when you only have a list of profile id's for debug.|| This profile example uses the JDK version to trigger activation, and provides a JDK-specific repo.<profile><id>jdk-1.4</id><activation><jdk>1.4</jdk></activation><repositories><repository><id>jdk14</id><name>Repository for JDK 1.4 builds</name><url>http://www.myhost.com/maven/jdk14</url><layout>default</layout><snapshotPolicy>always</snapshotPolicy></repository></repositories></profile>--><!--| Here is another profile, activated by the system property 'target-env' with a value of 'dev',| which provides a specific path to the Tomcat instance. To use this, your plugin configuration| might hypothetically look like:|| ...| <plugin>|   <groupId>org.myco.myplugins</groupId>|   <artifactId>myplugin</artifactId>||   <configuration>|     <tomcatLocation>${tomcatPath}</tomcatLocation>|   </configuration>| </plugin>| ...|| NOTE: If you just wanted to inject this configuration whenever someone set 'target-env' to|       anything, you could just leave off the <value/> inside the activation-property.|<profile><id>env-dev</id><activation><property><name>target-env</name><value>dev</value></property></activation><properties><tomcatPath>/path/to/tomcat/instance</tomcatPath></properties></profile>--></profiles><!-- activeProfiles| List of profiles that are active for all builds.|<activeProfiles><activeProfile>alwaysActiveProfile</activeProfile><activeProfile>anotherAlwaysActiveProfile</activeProfile></activeProfiles>-->
</settings>

按照下图把 User setting file的文件路径改成刚才保存的setting文件路径。

做完上面的之后，手动点一下下面的图表，重新加载pom（过程可能有点慢）

最后出现下图的结果配置就完成了。

2. 连接数据库

2.1 student类

package com.model;public class Student {private int id;private String sn;private String name;private String mail;private int classesId;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getSn() {return sn;}public void setSn(String sn) {this.sn = sn;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getMail() {return mail;}public void setMail(String mail) {this.mail = mail;}public int getClassesId() {return classesId;}public void setClassesId(int classesId) {this.classesId = classesId;}@Overridepublic String toString() {return "Student{" +"id=" + id +", sn='" + sn + '\'' +", name='" + name + '\'' +", mail='" + mail + '\'' +", classesId=" + classesId +'}';}
}

2.2 Demo01_Connection类

package com;import com.model.Student;import com.mysql.cj.jdbc.MysqlDataSource;import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Scanner;public class Demo01_Connection {// 先定义一个数据源对象private static DataSource dataSource = null;// 数据库的用户名private static final String USER = "root";// 数据库的密码private static final String PASSWORD = "123456";// 数据库连接字符串private static final String URL = "jdbc:mysql://127.0.0.1:3306/myjava?characterEncoding=utf-8&useSSL=false&serverTimezone=Asia/Shanghai";public static void main(String[] args) {// 1. 初化始数据源MysqlDataSource myDataSourse = new MysqlDataSource();// 2. 设置连接的参数myDataSourse.setURL(URL);myDataSourse.setUser(USER);myDataSourse.setPassword(PASSWORD);// 3. 把构建好的Mysql数据源赋值给JDBC中的datasourcedataSource = myDataSourse;Connection connection = null;// 预处理对象//Statement statement = null;//危险PreparedStatement statement = null;ResultSet resultSet = null;try{// 1. 通过数据源获取一个数据库连接connection = dataSource.getConnection();// 接收用户输入的值System.out.println("请输入学号：");Scanner scanner = new Scanner(System.in);String sn = scanner.next();// 2. 定义SQL语句
//            String sql = "select * from student where sn = '" + sn +"'";//危险操作String sql = "select * from student where sn = ?";//？为占位符System.out.println(sql);// 3. 获取statement对象
//            statement = connection.createStatement();// 获取一个预处理对象statement = connection.prepareStatement(sql);// 处理占位符的值statement.setString(1,sn);// 4. 执行SQLresultSet = statement.executeQuery();// 5. 解析结果集,resultSet.next()表示结果集中是否有记录if(resultSet.next()){// 创建表示结果的JAVA对象Student student = new Student();// 依次读取结果集中的数据并赋值给JAVA对象student.setId(resultSet.getInt(1));student.setSn(resultSet.getString(2));student.setName(resultSet.getString(3));student.setMail(resultSet.getString(4));student.setClassesId(resultSet.getInt(5));// 打印结果System.out.println(student);}} catch (SQLException e) {throw new RuntimeException(e);} finally {// 依次关闭资源if (resultSet != null) {try {resultSet.close();} catch (SQLException e) {e.printStackTrace();}}if (statement != null) {try {statement.close();} catch (SQLException e) {e.printStackTrace();}}if (connection != null) {try {connection.close();} catch (SQLException e) {e.printStackTrace();}}}}
}

2.3 测试结果