本例子包含了对数据库表简单的增删改查的操作,并且包含事物。该例子只适用于MySQL数据库。该例子需要手动创建数据库以及数据库表
例子中所需要的jar包,详查MyBatis---简介
一个entity类Student.java:这个类包含一个无参的构造函数,以及所有属性的getset方法
private static final long serialVersionUID = 2257468553009291835L; private int id; private String name; private int age; public Student() { } public Student(String name, int age) { super(); this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; }
一个MyBatis配置文件MyBatisConfig.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> <!-- 为entity类创建别名 --> <typeAliases> <typeAlias alias="Student" type="com.studyMyBatis.entity.Student"/> </typeAliases> <!-- 数据库配置 --> <environments default="development"> <environment id="development"> <transactionManager type="JDBC" /><!-- 设置事物采用JDBC处理方式,另一种处理方式为MANAGED --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/jsp_db"/> <property name="username" value="root"/> <property name="password" value="Lfq,909475"/> </dataSource> </environment> </environments> <!-- 关联mappers,每一个entity类都应有一个对应的mapper.xml文件,该文件用于存放操作数据库语句,相当于将sql保存到配置文件中,java直接调用即可 --> <mappers> <mapper resource="com/studyMyBatis/map/student.xml" /> </mappers> </configuration>
输出日志信息配置log4j.properties:该配置文件中设置sql显示级别为DEBUG,显示在控制台中
log4j.rootLogger=DEBUG, Console #Console log4j.appender.Console=org.apache.log4j.ConsoleAppender log4j.appender.Console.layout=org.apache.log4j.PatternLayout log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%n log4j.logger.java.sql.ResultSet=INFO log4j.logger.org.apache=INFO log4j.logger.java.sql.Connection=DEBUG log4j.logger.java.sql.Statement=DEBUG log4j.logger.java.sql.PreparedStatement=DEBUG
一个与entity类Student.java对应的mapper文件student.xml:文件中所有的#{值}应与传过来的对象中的属性名称或HashMap中键的名称相同。如:#{name},那么传过来的Student中就必须有name属性,或传过来的HashMap中有键为name的值
<?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="/"> <!-- 添加成功,会返回插入数据的主键id到student对象中。但需要数据库支持主键id自增长,比如oracle就不能返回 --> <insert id="insertStudent" parameterType="Student" statementType="PREPARED" keyProperty="studentId" useGeneratedKeys="true"> insert into Student (name,age) values(#{name},#{age}) </insert> <update id="updateStudentById" parameterType="Student"> update student set name=#{name}, age=#{age} where studentId = #{studentId} </update> <delete id="deleteStudentById" parameterType="Student"> delete from student where studentId = #{studentId} </delete> <select id="getStudentById" parameterType="int" resultType="Student"> select * from student where studentId=#{studentId} </select> <select id="getStudentByEntity" parameterType="Student" resultType="Student"> select * from student where studentId=#{studentId} </select> <select id="getStudentByNameAndAge" parameterType="hashmap" resultType="Student"> select * from student where name=#{name} and age=#{age} </select> <select id="getStudentResultHashMapById" parameterType="int" resultType="hashmap"> select * from student where studentId=#{studentId} </select> <select id="getAllStudents" resultType="Student"> select * from student </select> <resultMap type="Student" id="StudentMap"> <id property="studentId" column="studentId" /> <result property="name" column="name" /> <result property="age" column="age" /> </resultMap> <select id="getStudent" parameterType="int" resultMap="StudentMap"> select * from student where studentId=#{studentId} </select>
</mapper>
一个测试类
public class Test { public static void main(String[] args) { Reader reader = null; SqlSession sqlSession = null; try { String resoutce = "com/studyMyBatis/map/MyBatisConfig.xml"; reader = Resources.getResourceAsReader(resoutce); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader); sqlSession = sqlSessionFactory.openSession(false);//参数设置是否自动提交,默认false(相当于事物管理) new Test().insertStudent(sqlSession); sqlSession.commit(); } catch (Exception e) { e.printStackTrace(); if (sqlSession != null) { sqlSession.rollback(); } } finally { if (sqlSession != null) { sqlSession.close(); } } } /** 添加一条数据 * @param sqlSession * @return 返回插入的这条数据的主键id */ public int insertStudent(SqlSession sqlSession) { Student student = new Student("王五", 24); sqlSession.insert("insertStudent", student); return student.getId(); } /** 根据id修改一条数据 * @param sqlSession */ public void updateStudentById(SqlSession sqlSession) { Student student = new Student("张三改", 24); student.setId(3); sqlSession.update("updateStudentById", student); } /** 根据id删除一条数据 * @param sqlSession */ public void deleteStudentById(SqlSession sqlSession) { Student student = new Student(); student.setId(4); sqlSession.delete("deleteStudentById", student); } /** 根据id查询一条Student记录 * @param sqlSession * @param studentId Student.id * @return */ public Student getStudentById(SqlSession sqlSession, int studentId) { return sqlSession.selectOne("getStudentById", studentId); } /** 根据Student对象查询一条Student记录 * @param sqlSession * @param student 该对象中至少应包括查询语句中的条件字段的值 * @return */ public Student getStudentByEntity(SqlSession sqlSession, Student student) { return sqlSession.selectOne("getStudentByEntity", student); } /** 根据一个HashMap查询一条Student记录 * @param sqlSession * @return */ public Student getStudentByNameAndAge(SqlSession sqlSession, HashMap<String, Object> hashMap) { return sqlSession.selectOne("getStudentByNameAndAge", hashMap); } /** 根据id查询一条Student记录 * @param sqlSession * @param studentId Student.id * @return */ public HashMap<String, Object> getStudentResultHashMapById(SqlSession sqlSession, int studentId) { return sqlSession.selectOne("getStudentResultHashMapById", studentId); } /** 查询所有的Student记录 * @param sqlSession * @return List<Student> */ public List<Student> getAllStudents(SqlSession sqlSession){ return sqlSession.selectList("getAllStudents"); } /*-------------------------------------------------------------------------------------------------------------------------* *---------------------------------------以上是设置参数属性为parameterType-------------------------------------------------* *------------------------------------查询多条记录设置参数与查询一条记录相同-----------------------------------------------* *--------------------返回值数据类型也可是一个HashMap,即设置resultType属性即可,一般用于联合查询--------------------------* *------------------------resultMap就不写java代码了,在xml中最后有介绍,其它用法都差不多-----------------------------------* *-------------------------------------------------------------------------------------------------------------------------*/ }
查询语句<select>标签的属性描述
属性 | 描述 |
id | 在命名空间中唯一的标识符,可以被用来引用这条语句 |
parameterType | 将会传入这条语句的参数类的完全限定名或别名或一个hashmap |
parameterMap | 这是引用外部parameterMap的已经被废弃的方法。适用内联参数映射和parameterType属性 |
resultType | 从这条语句中返回的期望类型的类的完全限定名或别名。注意集合情形,那应该是集合可以包含的类型,而不是集合。使用resultType或resultMap,但不能同时使用 |
resultMap | 命名引用外部的resultMap。返回map是MyBatis最具力量的特性,对其有一个很好的理解的话,许多复杂映射的情形就能被解决了。使用resultMap或resultType,但不能同时使用 |
flushCache | 将其设置为true,不论语句什么时候被调用,都会导致缓存被清空。默认值为false |
useCache | 将其设置为true,将会导致本条语句的结果被缓存。默认值为true |
timeout | 这个设置驱动程序等待数据库返回请求结果,并抛出异常事件的最大等待之。默认不设置(驱动自行处理) |
fetchSize | 这是暗示驱动程序每次批量返回的结果行数。默认不设置(驱动自行处理) |
statementType | STATEMENT,PREPARED或CALLABLE的一种。这会让MyBatis使用选择使用Statement,preparedStatement或CallableStatement,默认值:PREPARED |
resultSetType | FORWAARE_ONLY|SCROLL_SENSITIVE|SCROLL_INSENSITIVE中的一种。默认不设置(驱动自行处理) |