MyBatis Plus 2.3 个人笔记-02-基本注解
- 实体类注解
/*
* MybatisPlus会默认使用实体类的类名到数据中找对应的表.
*
*/
@TableName("tbl_employee")
public class Employee extends Model<Employee> {
private static final long serialVersionUID = 1L;
/*
* @TableId:
* value: 指定表中的主键列的列名， 如果实体属性名与列名一致，可以省略不指定.
* type: 指定主键策略. ID_WORKER 全局唯一ID，内容为空自动填充（默认配置）
*/
@TableId(value = "id", type = IdType.ID_WORKER)
private Long id;
private String lastName;
private String email;
private String gender;
private Integer age;
/**
* 声明该属性不是数据库中字段
*/
@TableField(exist = false)
private String notExist;
}
/* 省略get set */
- 使用通用CURD方法
- 删除
/**
* 通用 删除操作
*/
@Test
public void testCommonDelete() {
//1 .根据id进行删除
Integer result = employeeMapper.deleteById(13);
/*
==> Preparing: DELETE FROM tbl_employee WHERE id=?
==> Parameters: 13(Long)
<== Updates: 0
*/
//2. 根据 条件进行删除
// Map<String,Object> columnMap = new HashMap<>();
// columnMap.put("last_name", "MP");
// columnMap.put("email", "mp@atguigu.com");
// Integer result = employeeMapper.deleteByMap(columnMap);
// System.out.println("result: " + result );
/*
==> Preparing: DELETE FROM tbl_employee WHERE last_name = ? AND email = ?
==> Parameters: MP(String), mp@atguigu.com(String)
<== Updates: 0
*/
//3. 批量删除
// List<Integer> idList = new ArrayList<>();
// idList.add(3);
// idList.add(4);
// idList.add(5);
// Integer result = employeeMapper.deleteBatchIds(idList);
// System.out.println("result: " + result );
}
/*
==> Preparing: DELETE FROM tbl_employee WHERE id IN ( ? , ? , ? )
==> Parameters: 35(Integer), 45(Integer), 55(Integer)
<== Updates: 0
*/
条件构造器
实体包装器，用于处理 sql 拼接，排序，实体参数查询等！
补充说明： 使用的是数据库字段，不是Java属性!
/**
* 条件构造器 删除操作
*
*/
@Test
public void testEntityWrapperDelete() {
employeeMapper.delete(
new EntityWrapper<Employee>()
.eq("last_name", "Tom")
.eq("age", 22)
);
}
/*
==> Preparing: DELETE FROM tbl_employee WHERE (last_name = ? AND age = ?)
==> Parameters: Tom(String), 22(Integer)
<== Updates: 0
*/
-
- 修改
- 修改
/**
* 通用 更新操作
*/
@Test
public void testCommonUpdate() {
//初始化修改对象
Employee employee = new Employee();
employee.setId(7L);
employee.setLastName("小泽老师");
employee.setEmail("xz@sina.com");
employee.setGender("0");
// updateById 实体类为空的列 自动跳出，不修改
Integer result = employeeMapper.updateById(employee);
/*
==> Preparing: UPDATE tbl_employee SET last_name=?, email=?, gender=? WHERE id=?
==> Parameters: 小泽老师(String), xz@sina.com(String), 0(String), 7(Long)
<== Updates: 0
*/
// updateAllColumnById 所有列都会修改
Integer result = employeeMapper.updateAllColumnById(employee);
/*
==> Preparing: UPDATE tbl_employee SET last_name=?,email=?,gender=?,age=?,version=? WHERE id=?
==> Parameters: 小泽老师(String), xz@sina.com(String), 0(String), null, null, 7(Long)
<== Updates: 0
*/
}
/**
* 条件构造器 修改操作
*/
@Test
public void testEntityWrapperUpdate() {
Employee employee = new Employee();
employee.setLastName("苍老师");
employee.setEmail("cls@sina.com");
employee.setGender("0");
employeeMapper.update(employee,
new EntityWrapper<Employee>()
.eq("last_name", "Tom")
.eq("age", 44)
);
/*
==> Preparing: UPDATE tbl_employee SET last_name=?, email=?, gender=? WHERE (last_name = ? AND age = ?)
==> Parameters: 苍老师(String), cls@sina.com(String), 0(String), Tom(String), 44(Integer)
<== Updates: 0
*/
}
-
- 新增
/**
* 通用 插入操作
*/
@Test
public void testCommonInsert() {
//初始化Employee对象
Employee employee = new Employee();
employee.setLastName("MP");
employee.setEmail("mp@atguigu.com");
//employee.setGender(1);
//employee.setAge(22);
//employee.setSalary(2"0""0""0""0"."0");
//插入到数据库
// insert方法在插入时， 会根据实体类的每个属性进行非空判断，只有非空的属性对应的字段才会出现到SQL语句中
//Integer result = employeeMapper.insert(employee);
/*
==> Preparing: INSERT INTO tbl_employee ( id, last_name, email ) VALUES ( ?, ?, ? )
==> Parameters: 1107953008443265026(Long), MP(String), mp@atguigu.com(String)
<== Updates: 1
*/
//insertAllColumn方法在插入时， 不管属性是否非空， 属性所对应的字段都会出现到SQL语句中.
Integer result = employeeMapper.insertAllColumn(employee);
/*
==> Preparing: INSERT INTO tbl_employee ( id,last_name,email,gender,age,version ) VALUES ( ?,?,?,?,?,? )
==> Parameters: 1107952717069209602(Long), MP(String), mp@atguigu.com(String), null, null, null
<== Updates: 1
*/
System.out.println("result: " + result );
//获取当前数据在数据库中的主键值 mybatis plus自动会回填id
Long key = employee.getId();
System.out.println("key:" + key );
}
-
- 查询
/**
* 通用 查询操作
*/
@Test
public void testCommonSelect() {
//1. 通过id查询
// Employee employee = employeeMapper.selectById(7);
// System.out.println(employee);
//2. 通过多个列进行查询 id + lastName
// Employee employee = new Employee();
// //employee.setId(7);
// employee.setLastName("小泽老师");
// employee.setGender("0");
//
// Employee result = employeeMapper.selectOne(employee);
// System.out.println("result: " +result );
//3. 通过多个id进行查询 <foreach>
// List<Integer> idList = new ArrayList<>();
// idList.add(4);
// idList.add(5);
// idList.add(6);
// idList.add(7);
// List<Employee> emps = employeeMapper.selectBatchIds(idList);
// System.out.println(emps);
//4. 通过Map封装条件查询
// Map<String,Object> columnMap = new HashMap<>();
// columnMap.put("last_name", "Tom");
// columnMap.put("gender", 1);
//
// List<Employee> emps = employeeMapper.selectByMap(columnMap);
// System.out.println(emps);
//5. 分页查询
List<Employee> emps = employeeMapper.selectPage(new Page(1, 2), null);
System.out.println(emps);
}
/**
* 条件构造器 查询操作
*/
@Test
public void testEntityWrapperSelect() {
//我们需要分页查询tbl_employee表中，年龄在18~5"0"之间且性别为男且姓名为Tom的所有用户
// List<Employee> emps =employeeMapper.selectPage(new Page<Employee>(1, 2),
// new EntityWrapper<Employee>()
// .between("age", 18, 5"0")
// .eq("gender", 1)
// .eq("last_name", "Tom")
// );
// System.out.println(emps);
/*
==> Preparing: SELECT COUNT(1) FROM tbl_employee WHERE (age BETWEEN ? AND ? AND gender = ? AND last_name = ?)
==> Parameters: 18(Integer), 50(Integer), 1(Integer), Tom(String)
<== Columns: COUNT(1)
<== Row: 0
==> Preparing: SELECT id AS id,last_name AS lastName,email,gender,age,version FROM tbl_employee WHERE (age BETWEEN ? AND ? AND gender = ? AND last_name = ?)
==> Parameters: 18(Integer), 50(Integer), 1(Integer), Tom(String)
<== Total: 0
*/
// 查询tbl_employee表中， 性别为女并且名字中带有"老师" 或者 邮箱中带有"a"
// List<Employee> emps = employeeMapper.selectList(
// new EntityWrapper<Employee>()
// .eq("gender", "0")
// .like("last_name", "老师")
// //.or() // SQL: (gender = ? AND last_name LIKE ? OR email LIKE ?)
// .orNew() // SQL: (gender = ? AND last_name LIKE ?) OR (email LIKE ?)
// .like("email", "a")
// );
// System.out.println(emps);
/*
==> Preparing: SELECT id AS id,last_name AS lastName,email,gender,age,version FROM tbl_employee WHERE (gender = ? AND last_name LIKE ?) OR (email LIKE ?)
==> Parameters: 0(String), %老师%(String), %a%(String)
<== Columns: id, lastName, email, gender, age, version
<== Row: 1107952717069209602, MP, mp@atguigu.com, null, null, null
<== Row: 1107953008443265026, MP, mp@atguigu.com, null, null, null
<== Total: 2
*/
// 查询性别为女的, 根据age进行排序(asc/desc), 简单分页
// List<Employee> emps = employeeMapper.selectList(
// new EntityWrapper<Employee>()
// .eq("gender", "0")
// .orderBy("age")
// //.orderDesc(Arrays.asList(new String [] {"age"}))
// .last("desc limit 1,3")
// );
// System.out.println(emps);
}
/*
==> Preparing: SELECT id AS id,last_name AS lastName,email,gender,age,version FROM tbl_employee WHERE (gender = ?) ORDER BY age desc limit 1,3
==> Parameters: 0(String)
<== Total: 0
*/
