MyBatis的CURD

Mybatis 数据库增删改查操作：

数据准备

MyBatis的CURD

MyBatis的CURD

项目结构

MyBatis的CURD

Department

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
 
package com.hph.mybatis.beans;

import java.util.List;

public class Department {

    private Integer id;
    private String departmentName ;

    private List<Employee> emps ;


    public List<Employee> getEmps() {
        return emps;
    }
    public void setEmps(List<Employee> 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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
 
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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
 

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<String, Object> map);

    //查询多个数据返回一个对象的集合
    public List<Employee>  getEmps();

    //查询单条数据返回一个Map
    public Map<String,Object> 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<Integer,Employee> getEmpsRetrunMap();

}
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
 
<?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">
<!--配置SQL映射-->
<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>
    <!--public Employee getEmployeeById(Integer id);-->
    <select id="getEmployeeById" resultType="com.hph.mybatis.beans.Employee">
		select id, last_name , email, gender from tbl_employee where id = #{id}
    </select>
    <!--public void addEmployee(Employee employee);
  parameterType:指定ca参数类型,可以省略不写
  keyProperty:指定用对象的那个属性ba保存mybatisf返回的主键值
    -->
    <!--告诉mybatis:需要使用主键自增的方式-->
    <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>
    <!--public List<Employee>  getEmps()
    resultType结果集的封装类型
    ;-->
    <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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
 
<?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">
<!--配置SQL映射-->
<mapper namespace="com.hph.mybatis.dao.EmployeeMapper">

    <!--public Employee getEmployeeById(Integer id);-->
    <select id="getEmployeeById" resultType="com.hph.mybatis.beans.Employee">
		select id, last_name , email, gender from tbl_employee where id = #{id}
    </select>
    <!--public void addEmployee(Employee employee);
  parameterType:指定ca参数类型,可以省略不写
  keyProperty:指定用对象的那个属性ba保存mybatisf返回的主键值
    -->
    <!--告诉mybatis:需要使用主键自增的方式-->
    <insert id="addEmployee" useGeneratedKeys="true" keyProperty="id">
  insert  into  tbl_employee(last_name,email,gender) values (#{lastName},#{email},#{gender})
    </insert>


    <!--public void updateEmployee(Employee employee);-->
    <update id="updateEmployee">
	update tbl_employee set
		last_name = #{lastName},
		email = #{email},
		gender = #{gender}
		where id = #{id}
    </update>

    <!--public Integer deleteEmployeeById(Integer id);-->
    <delete id="deleteEmployeeById">
        delete  from  tbl_employee where id = #{id}
    </delete>
    <!--    public Employee getEmployeeByIdAndLastName(@Param("id") Integer id, @Param("lastName") String lastNmae);
-->
    <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>
    <!--public Employee getEmployeeByMap(Map<String, Object> map);-->
    <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>
    <!--public List<Employee>  getEmps()
    resultType结果集的封装类型
    ;-->
    <!--public List<Employee>  getEmps();-->
    <select id="getEmps" resultType="com.hph.mybatis.beans.Employee">
		select id, last_name , email, gender from tbl_employee
    </select>
    <!--public Map<String,Object> getEmployeeByIdReturnMap(Integer id);-->
    <select id="getEmployeeByIdReturnMap" resultType="java.util.Map">

		select id, last_name , email, gender from tbl_employee where  id = #{id}

    </select>
    <!--public Map<Integer,Employee> getEmpsRetrunMap();-->
    <select id="getEmpsRetrunMap" resultType="java.util.Map">
		select id, last_name , email, gender from tbl_employee
    </select>
</mapper>

TestMybatisMapper

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
 
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<String, Object> map = new HashMap<String, Object>();
            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<Employee> emps = mapper.getEmps();
            //System.out.println(emps);
            //Map<String, Object> map = mapper.getEmployeeByIdReturnMap(5);
            //System.out.println(map);
            Map<Integer, Employee> map = mapper.getEmpsRetrunMap();
            System.out.println(map);
        } finally {
            session.close();
        }
    }
}

结果

testHelloWorldMapper

MyBatis的CURD

addEmployee

添加数据

MyBatis的CURD

MyBatis的CURD

修改数据

MyBatis的CURD

MyBatis的CURD

删除数据

MyBatis的CURD

MyBatis的CURD

testParameter

MyBatis的CURD

tetSelect

无参数

MyBatis的CURD

有参数

MyBatis的CURD

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。

1
2
3
4
5
6
7
 
<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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
 
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<String, Object> param = new ParamMap<Object>();
      int i = 0;
      for (Map.Entry<Integer, String> entry : names.entrySet()) {
        param.put(entry.getValue(), args[entry.getKey()]);
        // add generic param names (param1, param2, ...)
        final String genericParamName = GENERIC_NAME_PREFIX + String.valueOf(i + 1);
        // ensure not to overwrite parameter named with @Param
        if (!names.containsValue(genericParamName)) {
          param.put(genericParamName, args[entry.getKey()]);
        }
        i++;
      }
      return param;
    }
  }

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

1
2
3
4
5
6
7
8
9
 
#{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<Employee> getAllEmps();

查询单行数据返回Map集合

1
 
public Map<String,Object> 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<Integer,Employee>  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

相关文章：

  • 2022-12-23
  • 2022-12-23
  • 2022-12-23
  • 2021-04-27
  • 2022-12-23
  • 2022-12-23
  • 2021-12-13
  • 2021-05-15
猜你喜欢
  • 2021-08-01
  • 2021-10-10
  • 2021-09-11
  • 2022-12-23
  • 2022-12-23
  • 2021-08-27
相关资源
相似解决方案
热门标签
Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode