* JDBC例子
* 前期准备,构建数据库,构建表,插入数据
* 添加依赖
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.16</version>
</dependency>
</dependencies>
* 代码
/**
* Hello world!
*
*/
public class App
{
public static void main( String[] args )
{
// 1 加载驱动
Connection conn=null;
PreparedStatement pstm=null;
ResultSet rs=null;
try {
Class.forName("com.mysql.jdbc.Driver");
// 2 获得链接
String url="jdbc:mysql://localhost:3306/hx01?characterEncoding=utf-8";
String usrename="root";
String psw="root";
conn = DriverManager.getConnection(url, usrename, psw);
// 3 定义sql
String sql="SELECT * FROM USER WHERE sex=?";
// 4 获得statement
pstm = conn.prepareStatement(sql);
pstm.setString(1,"男");
// 5 获得结果或者执行
rs = pstm.executeQuery();
while (rs.next()){
String name = rs.getString(2);
System.out.println(name);
}
// 6 关闭资源
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}finally {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
;
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
* 直接使用原生JDBC问题分析
问题
1、在创建连接时,存在硬编码
解决方法: 配置文件(全局配置文件)
2、在执行statement时存在硬编码(存在sql语句)
解决方法:配置文件(映射文件)
3、频繁的开启和关闭数据库连接,会造成数据库性能下降。
解决方法: 数据库连接池(全局配置文件)
* MyBatis简介
* 框架:软件开发半成品
* 什么是 MyBatis ?(以前叫IBatis)
MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解,将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。
* Hello Mybatis
* http://www.mybatis.org/mybatis-3/getting-started.html
* 添加依赖
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.16</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.3.0</version>
</dependency>
</dependencies>
* 创建全局配置文件(SqlMapConfig)
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url"
value="jdbc:mysql://localhost:3306/hx01?characterEncoding=utf-8" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mapper/User.xml" />
</mappers>
</configuration>
* 创建sql描述文件(User.xml)
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="hx">
<select id="findUserNameBySex" resultType="string">
SELECT username FROM
USER WHERE sex=#{sex}
</select>
</mapper>
* 编写代码
@Test
public void testFindUsernameBySex() throws Exception {
// 1 声明全局配置文件
String resource = "SqlMapConfig.xml";
// 2 获取的全局配置文件的输入流
InputStream is = Resources.getResourceAsStream(resource);
// 3 创建SqlSessionFactory
SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(is);
// 4 创建SqlSession
SqlSession slqSession=ssf.openSession();
// 5 调用SqlSession的查询方法
List<String> userNames = slqSession.selectList("hx.findUserNameBySex", "男");
// 6 迭代userName列表
for(String name:userNames) {
System.out.println(name);
}
// 7 关闭资源
slqSession.close();
}
* JDBC连接所需参数配置到dbconfig.properties中
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/hx01?characterEncoding=utf-8
username=root
password=root
* 添加日志框架
了解SLF4J
* SLF4J没有真正地实现日志记录
知道SLF4J与Log4j,logback,..等等区别
* 一个抽象,其他具体的(就像jdbc与mysql驱动,Oracle驱动)
* https://www.oschina.net/translate/why-use-sl4j-over-log4j-for-logging
* 添加依赖
<!--slf4j-->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.25</version>
</dependency>
<!--log4j-->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<!--slf4j到log4j-->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.25</version>
</dependency>
* 创建log4j.properties文件
log4j.rootLogger=debug, stdout, R
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p - %m%n
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=firestorm.log
log4j.appender.R.MaxFileSize=100KB
log4j.appender.R.MaxBackupIndex=1
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n
log4j.logger.com.codefutures=DEBUG