所需的maven依賴

<dependencies><!-- Mybatis核心 --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.7</version></dependency><!-- junit測試 --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency><!-- MySQL驅動 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.16</version></dependency><!-- lombok，自己生成實體類的getter和setter以及toString等方法 --><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency> </dependencies>

模糊查詢的三種實現方式

MybatisSQL語句一

此寫法是錯誤的，此寫法會報如下的錯誤，原因是"%#{mohu}%"中的“#”號會被mybatis解析為占位符“？”從而導致SQL語句出錯，編譯后的SQL語句變成了

select * from t_user where username like "%?%"

這與預期的結果不一致，自然就會報如下的錯誤，該寫法要特別注意%和#的位置

<!--錯誤的寫法--> <select id="getUserByLike" resultType="User">select * from t_user where username like "%#{mohu}%" </select>

方式一正確的寫法

<select id="getUserByLike" resultType="User">select * from t_user where username like "%"#{mohu}"%" </select>

MybatisSQL語句二

<select id="getUserByLike" resultType="User">select * from t_user where username like '%${mohu}%' </select>

MybatisSQL語句三

<select id="getUserByLike" resultType="User">select * from t_user where username like concat('%',#{mohu},'%')</select>

mapper層接口

public interface SpecialSQLMapper {/*** 通過用戶名模糊查詢用戶信息* @param mohu* @return*/List<User> getUserByLike(@Param("mohu") String mohu); }

注意：select標簽中的id必須是mapper接口的方法名，resultType可以是實體類起別名后的名稱，要不然就是實體類的全限定名稱,即（com.xxx.entity.xxx,若resultType使用別名時必須在mybatis的核心配置文件配置如下

mybatis的核心配置文件

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration><!--MyBatis核心配置文件中的標簽必須要按照指定的順序配置：properties?,settings?,typeAliases?,typeHandlers?,objectFactory?,objectWrapperFactory?,reflectorFactory?,plugins?,environments?,databaseIdProvider?,mappers?--><typeAliases><package name="com.example.mybatis.entity"/></typeAliases><!--引入mybatis的映射文件--><mappers><package name="com.example.mybatis.mapper"/></mappers> </configuration>

實體類

@Data public class User {private Integer id;private String username;private String password;private Integer age;private String gender;private String email; }

工具類

public class SqlSessionUtil {public static SqlSession getSqlSession(){SqlSession sqlSession = null;try {//獲取核心配置文件的輸入流InputStream is = Resources.getResourceAsStream("mybatis-config.xml");//獲取SqlSessionFactoryBuilderSqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();//獲取SqlSessionFactorySqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);//獲取SqlSession對象sqlSession = sqlSessionFactory.openSession(true);} catch (IOException e) {e.printStackTrace();}return sqlSession;}}

測試

public class SpecialSQLMapperTest {@Testpublic void testGetUserByLike(){SqlSession sqlSession = SqlSessionUtil.getSqlSession();SpecialSQLMapper mapper = sqlSession.getMapper(SpecialSQLMapper.class);List<User> list = mapper.getUserByLike("a");list.forEach(System.out::println);} }

總結

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