主要搭建過程
1. pom.xml文件中加入mybatis和數據庫依賴，這里使用mysql：
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<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啟動要加載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. 在類路徑下創建mybatis的配置文件Configuration.xml
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<?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><!-- 別名 --> <typeAlias alias="User" type="com.john.hbatis.model.User" /> </typeAliases> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"><!-- 數據源 --> <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. 執行創建數據庫和表的sql：
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-- 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類：
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public class User { private int id; private String name; private String age; private String address; // Getters and setters are omitted // 如果有帶參數的構造器，編譯器不會自動生成無參構造器。當查詢需要返回對象時，ORM框架用反射來調用對象的無參構造函數，導致異常：java.lang.NoSuchMethodException: com.john.hbatis.model.User.<init>() // 這時需要明確寫出： 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路徑下的User.xml
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<?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. 測試類：
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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()); } } |
以接口方式交互數據
上面的環境搭建是采用SqlSession的通用方法并強制轉換的方式，存在著轉換安全的問題：
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User user = (User)session.selectOne("com.john.hbatis.model.UserMapper.getUserById", 1); |
可以采用接口加sql語句的方式來解決，sql語句理解為是接口的實現：
1. 新建接口類：
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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，確保namespace屬性值和接口的全限定名相同，且id屬性值和接口方法名相同：
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<mapper namespace="com.john.hbatis.mapper.IUserMapper"> <select id="getUserById" |
3. 在MyBatisBasicTest類中添加測試方法：
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@Testpublic 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，報org.apache.ibatis.binding.BindingException: Type interface com..IUserMapper is not known to the MapperRegistry異常。 User user = mapper.getUserById(1); log.info("{}: {}", user.getName(), user.getAddress()); } |
附：
上面的實現是把sql語句放在XML文件中，并通過一定的約束來保證接口能夠在XML中找到對應的SQL語句；
還有一種方式是通過接口+注解SQL方式來交互數據：
1. 新建接口類：
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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：
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<mappers> <mapper class="com.john.hbatis.mapper.IUserMapper2" /> </mappers> |
或在初始化語句中加入：
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sqlSessionFactory.getConfiguration().addMapper(IUserMapper2.class); |
3. 相應修改上面的測試方法：
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IUserMapper2 mapper = session.getMapper(IUserMapper2.class); |
