MyBatis的CURD

Mybatis 数据库增删改查操作：

数据准备

项目结构

Department

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package com.hph.mybatis.beans; import java.util.List; public class Department { private Integer id; private String departmentName ; private List emps ; public List getEmps() { return emps; } public void setEmps(List emps) { this.emps = emps; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getDepartmentName() { return departmentName; } public void setDepartmentName(String departmentName) { this.departmentName = departmentName; } @Override public String toString() { return "Department [id=" + id + ", departmentName=" + departmentName + "]"; } }

Employee

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package com.hph.mybatis.beans; public class Employee { private Integer id; private String lastName; private String email; private Integer gender; private Department dept; public void setDept(Department dept) { this.dept = dept; } public Department getDept() { return dept; } public Employee() { } public Employee(Integer id, String lastName, String email, Integer gender, Department dept) { this.id = id; this.lastName = lastName; this.email = email; this.gender = gender; this.dept = dept; } public Employee(Integer id, String lastName, String email, Integer gender) { super(); this.id = id; this.lastName = lastName; this.email = email; this.gender = gender; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public Integer getGender() { return gender; } public void setGender(Integer gender) { this.gender = gender; } @Override public String toString() { return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + "]"; } }

EmployeeMapper

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import com.hph.mybatis.beans.Employee; import org.apache.ibatis.annotations.MapKey; import org.apache.ibatis.annotations.Param; import java.util.List; import java.util.Map; public interface EmployeeMapper { //根据id查询员工 public Employee getEmployeeById(Integer id); //添加一个新的员工 public void addEmployee(Employee employee); //修改一个员工 public void updateEmployee(Employee employee); //删除一个员工 public Integer deleteEmployeeById(Integer id); //查询对象通过两个参数 public Employee getEmployeeByIdAndLastName(@Param("id") Integer id, @Param("lastName") String lastNmae); //查询一个集合 public Employee getEmployeeByMap(Map map); //查询多个数据返回一个对象的集合 public List getEmps(); //查询单条数据返回一个Map public Map getEmployeeByIdReturnMap(Integer id); //查询多条数据返回一个Map @MapKey("id") //指定使用对象那个属性作为Map的key public Map getEmpsRetrunMap(); }

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"http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.hph.mybatis.dao.EmployeeMapper"> <select id="selectEmployee" resultType="com.hph.mybatis.beans.Employee"> select id, last_name , email, gender from tbl_employee where id = #{id} select> <select id="getEmployeeById" resultType="com.hph.mybatis.beans.Employee"> select id, last_name , email, gender from tbl_employee where id = #{id} select> <insert id="addEmployee" useGeneratedKeys="true" keyProperty="id"> insert into tbl_employee(last_name,email,gender) values (#{lastName},#{email},#{gender}) insert> <update id="updateEmployee"> update tbl_employee set last_name = #{lastName}, email = #{email}, gender = #{gender} where id = #{id} update> <delete id="deleteEmployeeById"> delete from tbl_employee where id = #{id} delete> <select id="getEmployeeByIdAndLastName" resultType="com.hph.mybatis.beans.Employee"> select id, last_name lastName, email, gender from tbl_employee where id = #{id} and last_name = #{lastName} select> <select id="getEmployeeByMap" resultType="com.hph.mybatis.beans.Employee"> select id, last_name , email, gender from ${tableName} where id = ${id} and last_name = #{ln} select> <select id="getEmps" resultType="com.hph.mybatis.beans.Employee"> select id, last_name , email, gender from tbl_employee select> <select id="getEmployeeByIdReturnMap" resultType="java.util.Map"> select id, last_name , email, gender from tbl_employee where id = #{id} select> <select id="getEmpsRetrunMap" resultType="java.util.Map"> select id, last_name , email, gender from tbl_employee select> mapper>

EmployeeMapper.xml

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"http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.hph.mybatis.dao.EmployeeMapper"> <select id="getEmployeeById" resultType="com.hph.mybatis.beans.Employee"> select id, last_name , email, gender from tbl_employee where id = #{id} select> <insert id="addEmployee" useGeneratedKeys="true" keyProperty="id"> insert into tbl_employee(last_name,email,gender) values (#{lastName},#{email},#{gender}) insert> <update id="updateEmployee"> update tbl_employee set last_name = #{lastName}, email = #{email}, gender = #{gender} where id = #{id} update> <delete id="deleteEmployeeById"> delete from tbl_employee where id = #{id} delete> <select id="getEmployeeByIdAndLastName" resultType="com.hph.mybatis.beans.Employee"> select id, last_name lastName, email, gender from tbl_employee where id = #{id} and last_name = #{lastName} select> <select id="getEmployeeByMap" resultType="com.hph.mybatis.beans.Employee"> select id, last_name , email, gender from ${tableName} where id = ${id} and last_name = #{ln} select> <select id="getEmps" resultType="com.hph.mybatis.beans.Employee"> select id, last_name , email, gender from tbl_employee select> <select id="getEmployeeByIdReturnMap" resultType="java.util.Map"> select id, last_name , email, gender from tbl_employee where id = #{id} select> <select id="getEmpsRetrunMap" resultType="java.util.Map"> select id, last_name , email, gender from tbl_employee select> mapper>

TestMybatisMapper

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package com.hph.mybatis.test; import com.hph.mybatis.beans.Employee; import com.hph.mybatis.dao.EmployeeMapper; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.junit.Test; import java.io.IOException; import java.io.InputStream; import java.sql.SQLException; import java.util.HashMap; import java.util.Map; public class TestMybatisMapper { @Test public void testSqlsessionFactory() throws IOException { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); System.out.println(sqlSessionFactory); SqlSession session = sqlSessionFactory.openSession(); System.out.println(session); try { Employee employee = session.selectOne("selectEmployee", 5); System.out.println(employee); } finally { session.close(); } } @Test public void testHelloWorldMapper() throws IOException { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); SqlSession session = sqlSessionFactory.openSession(); try { //Mapper接口 dao接口 EmployeeMapper dao = session.getMapper(EmployeeMapper.class); Employee employee = dao.getEmployeeById(1001); System.out.println(employee); } finally { session.close(); } } public SqlSessionFactory getsqlSessionFactory() throws IOException { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); return sqlSessionFactory; } @Test public void testCRUD() throws IOException, SQLException { SqlSessionFactory ssf = getsqlSessionFactory(); SqlSession session = ssf.openSession(true); try { //获取代理实现类对象 mapper接口的代理实现类对象 EmployeeMapper mapper = session.getMapper(EmployeeMapper.class); //添加 Employee employee = new Employee(null, "清风笑_Test", "[email protected]", 1); mapper.addEmployee(employee); System.out.println("返回的键值" + employee.getId()); /** * Connection conn = null; * PreparedStatement ps = conn.prepareStatement("sql", PreparedStatement.RETURN_GENERATED_KEYS); * * ps.executeUpdate(); * ps.getGeneratedKeys(); * jdbc获取新插入的组件的数值 */ //修改 Employee employee1 = new Employee(null,"清风_笑丶", "[email protected]", 1); mapper.updateEmployee(employee1); //删除 // Integer count = mapper.deleteEmployeeById(1001); // System.out.println(count); } finally { session.close(); } } @Test public void testParameter() throws IOException { SqlSessionFactory ssf = getsqlSessionFactory(); SqlSession session = ssf.openSession(true); try { EmployeeMapper mapper = session.getMapper(EmployeeMapper.class); // Employee employee = mapper.getEmployeeByIdAndLastName(5, "清风_笑丶"); Map map = new HashMap(); map.put("id", "5"); map.put("ln", "清风_笑丶"); map.put("tableName", "tbl_employee"); Employee employee = mapper.getEmployeeByMap(map); System.out.println(employee); } finally { session.close(); } } @Test public void tetSelect() throws IOException { SqlSessionFactory ssf = getsqlSessionFactory(); SqlSession session = ssf.openSession(true); try { EmployeeMapper mapper = session.getMapper(EmployeeMapper.class); //List emps = mapper.getEmps(); //System.out.println(emps); //Map map = mapper.getEmployeeByIdReturnMap(5); //System.out.println(map); Map map = mapper.getEmpsRetrunMap(); System.out.println(map); } finally { session.close(); } } }

结果

testHelloWorldMapper

addEmployee

添加数据

修改数据

删除数据

testParameter

tetSelect

无参数

有参数

主键生成方式、获取主键值

主键生成方式

支持主键自增，例如MySQL数据库

不支持主键自增，例如Oracle数据库

获取主键值

数据库支持自动生成主键的字段（比如 MySQL 和 SQL Server），则可以设置 useGeneratedKeys=”true”，然后再把 keyProperty设置到目标属性上。

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<insert id="insertEmployee" parameterType="com.hph.mybatis.beans.Employee" databaseId="mysql" useGeneratedKeys="true" keyProperty="id"> insert into tbl_employee(last_name,email,gender) values(#{lastName},#{email},#{gender}) insert>

参数传递

参数传递的方式

• 单个参数: 可以接受基本类型，对象类型。这种情况MyBatis可直接使用这个参数，不需要经过任 何处理。
• 多个参数: 任意多个参数，都会被MyBatis重新包装成一个Map传入。Map的key是param1，param2，或者0，1…，值就是参数的值
• 命名参数: 为参数使用@Param起一个名字，MyBatis就会将这些参数封装进map中，key就是我们自己指定的名
• POJO: 当这些参数属于我们业务POJO时，直接传递POJO
• Map : 我们也可以封装多个参数为map，直接传递
• Collection/Array : 会被MyBatis封装成一个map传入, Collection对应的key是collection,Array对应的key是array. 如果确定是List集合，key还可以是list.

参数传递源码

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public Object getNamedParams(Object[] args) { final int paramCount = names.size(); if (args == null || paramCount == 0) { return null; } else if (!hasParamAnnotation && paramCount == 1) { return args[names.firstKey()]; } else { final Map param = new ParamMap

参数处理

参数位置支持的属性: javaType、jdbcType、mode、numericScale、resultMap、typeHandler、jdbcTypeName、expression

实际上通常被设置的是：可能为空的列名指定 jdbcType ,例如:

1	insert into orcl_employee(id,last_name,email,gender) values(employee_seq.nextval,#{lastName, ,jdbcType=NULL },#{email},#{gender})可以在全局配置文件指定为null 也可以像上面这面这样单独配置

参数获取方式

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#{key}：可取普通类型、POJO类型、多个参数、集合类型 获取参数的值，预编译到SQL中。安全。Preparedstatement ${key}：可取单个普通类型、POJO类型、多个参数、集合类型 注意：取单个普通类型的参数，${}中不能随便写 必须用_parameter _parameter是Mybatis的内置参数获取参数的值，拼接到SQL中。有SQL注入问题。Statement ORDER BY ${name} 原则：能用#{}取值就优先使用#{} 解决不了的使用${} e.g.原生的JDBC不支持占位符的地方 就可以使用${} e.g.Select column1,column2…from 表 where 条件 group by 组表示 having 条件 order by 排序字段 desc/asc limit X，X；

select查询的几种情况

查询单行数据返回单个对象

1	public Employee getEmployeeById(Integer id );

查询多行数据返回对象的集合

1	public List getAllEmps();

查询单行数据返回Map集合

1	public Map getEmployeeByIdReturnMap(Integer id );

查询多行数据返回Map集合

1 2	@MapKey("id") // 指定使用对象的哪个属性来充当map的key(对象的属性，而不是数据库的列) public Map getAllEmpsReturnMap();

resultType自动映射

• autoMappingBehavior默认是PARTIAL，开启自动映射的功能。唯一的要求是列名和javaBean属性名一致
• 如果autoMappingBehavior设置为null则会取消自动映射
• 数据库字段命名规范，POJO属性符合驼峰命名法，如A_COLUMNaColumn，我们可以开启自动驼峰命名规则映射功能，mapUnderscoreToCamelCase=true

缺点：多表查询 完成不了