Java+MyBatis+MySQL开发环境搭建流程详解
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2024-03-11 23:08:31
主要搭建过程
1. pom.xml文件中加入mybatis和数据库依赖，这里使用mysql：
主要搭建过程
1. pom.xml文件中加入mybatis和数据库依赖，这里使用mysql：
<properties>
<mybatis.version>3.2.3</mybatis.version>
<mysql.version>5.1.26</mysql.version>
<slf4j.api.version>1.7.5</slf4j.api.version>
<testng.version>6.8.7</testng.version>
</properties>
<dependencies>
<dependency>
<groupid>org.mybatis</groupid>
<artifactid>mybatis</artifactid>
<version>${mybatis.version}</version>
</dependency>
<!-- database driver -->
<dependency>
<groupid>mysql</groupid>
<artifactid>mysql-connector-java</artifactid>
<version>${mysql.version}</version>
</dependency>
<!-- mybatis启动要加载log4j -->
<dependency>
<groupid>org.slf4j</groupid>
<artifactid>slf4j-log4j12</artifactid>
<version>${slf4j.api.version}</version>
</dependency>
<!-- test -->
<dependency>
<groupid>org.testng</groupid>
<artifactid>testng</artifactid>
<version>${testng.version}</version>
</dependency>
</dependencies>
2. 在类路径下创建mybatis的配置文件configuration.xml
<?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>
<typealiases><!-- 别名 -->
<typealias alias="user" type="com.john.hbatis.model.user" />
</typealiases>
<environments default="development">
<environment id="development">
<transactionmanager type="jdbc"/>
<datasource type="pooled"><!-- 数据源 -->
<property name="driver" value="com.mysql.jdbc.driver" />
<property name="url" value="jdbc:mysql://localhost:3306/hbatis" />
<property name="username" value="root" />
<property name="password" value="123456" />
</datasource>
</environment>
</environments>
<mappers><!-- orm映射文件 -->
<mapper resource="com/john/hbatis/model/user.xml" />
</mappers>
</configuration>
3. 执行创建数据库和表的sql：
-- create the database named 'hbatis'.
-- it's ok to use `, not ok to use ' or " surrounding the database name to prevent it from being interpreted as a keyword if possible.
create database if not exists `hbatis`
default character set = `utf8`;
-- create a table named 'user'
create table `user` (
`id` int(11) not null auto_increment,
`name` varchar(50) default null,
`age` int(11) default null,
`address` varchar(200) default null,
primary key (`id`)
) engine=innodb auto_increment=2 default charset=utf8;
-- insert a test record
insert into `user` values ('1', 'john', '120', 'hangzhou,westlake');
4. com.john.hbatis.model.user类：
public class user {
private int id;
private string name;
private string age;
private string address;
// getters and setters are omitted
// 如果有带参数的构造器，编译器不会自动生成无参构造器。当查询需要返回对象时，orm框架用反射来调用对象的无参构造函数，导致异常：java.lang.nosuchmethodexception: com.john.hbatis.model.user.<init>()
// 这时需要明确写出：
public user() {
}
public user(int id, string address) {
this.id = id;
this.address = address;
}
public user(string name, int age, string address) {
this.name = name;
this.age = age;
this.address = address;
}
}
com/john/hbatis/model路径下的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="com.john.hbatis.model.usermapper">
<select id="getuserbyid" parametertype="int" resulttype="user">
select * from `user` where id = #{id}
</select>
</mapper>
5. 测试类：
public class mybatisbasictest {
private static final logger log = loggerfactory.getlogger(mybatisbasictest.class);
private static sqlsessionfactory sqlsessionfactory;
private static reader reader;
@beforeclass
public static void initial() {
try {
reader = resources.getresourceasreader("configuration.xml");
sqlsessionfactory = new sqlsessionfactorybuilder().build(reader);
} catch (ioexception e) {
log.error("error thrown while reading the configuration: {}", e);
} finally {
if (reader != null) {
try {
reader.close();
} catch (ioexception e) {
log.error("error thrown while closing the reader: {}", e);
}
}
}
}
@test
public void querytest() {
sqlsession session = sqlsessionfactory.opensession();
user user = (user)session.selectone("com.john.hbatis.model.usermapper.getuserbyid", 1);
log.info("{}: {}", user.getname(), user.getaddress());
}
}
以接口方式交互数据
上面的环境搭建是采用sqlsession的通用方法并强制转换的方式，存在着转换安全的问题：
user user = (user)session.selectone("com.john.hbatis.model.usermapper.getuserbyid", 1);
可以采用接口加sql语句的方式来解决，sql语句理解为是接口的实现：
1. 新建接口类：
package com.john.hbatis.mapper;
import com.john.hbatis.model.user;
public interface iusermapper {
user getuserbyid(int id);
}
2. 修改user.xml文件，确保namespace属性值和接口的全限定名相同，且id属性值和接口方法名相同：
<mapper namespace="com.john.hbatis.mapper.iusermapper"> <select id="getuserbyid"
3. 在mybatisbasictest类中添加测试方法：
@test
public void queryininterfacewaytest() {
sqlsession session = sqlsessionfactory.opensession();
iusermapper mapper = session.getmapper(iusermapper.class); // 如果namespace和接口全限定名不一致，报org.apache.ibatis.binding.bindingexception: type interface com..iusermapper is not known to the mapperregistry异常。
user user = mapper.getuserbyid(1);
log.info("{}: {}", user.getname(), user.getaddress());
}
附：
上面的实现是把sql语句放在xml文件中，并通过一定的约束来保证接口能够在xml中找到对应的sql语句；
还有一种方式是通过接口+注解sql方式来交互数据：
1. 新建接口类：
package com.john.hbatis.mapper;
import org.apache.ibatis.annotations.select;
import com.john.hbatis.model.user;
public interface iusermapper2 {
@select({ "select * from `user` where id = #{id}" })
user getuserbyid(int id);
}
2. 在configuration.xml文件中加入：
<mappers> <mapper class="com.john.hbatis.mapper.iusermapper2" /> </mappers>
或在初始化语句中加入：
sqlsessionfactory.getconfiguration().addmapper(iusermapper2.class);
3. 相应修改上面的测试方法：
iusermapper2 mapper = session.getmapper(iusermapper2.class);
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