Mybatis传递参数

原博文链接

1. 匿名参数，顺序传递参数

mapper:

List selectByGenderAndAge(Short gender,String age );

xml:

<select id="selectByGenderAndAge" resultMap="BaseResultMap" >
  select * from employee where gender = #{0} and age = #{1}
select>

2.  使用@Param注解

mapper:

List selectByGenderAndAge( @Param("gender") Short gender,@Param("age") String age );

xml:

<select id="selectByGenderAndAge" resultMap="BaseResultMap" >
  select * from employee where gender = #{gender} and age = #{age}
select>

3. 使用map传递参数

mapper：

List selectByMapParams(Map params);

xml:

<select id="selectByMapParams" resultMap="BaseResultMap" parameterType="map">
  select * from employee where gender = #{gender} and age = #{age}
select>

4. 如果参数是 pojo，即实体类

mapper:

List  selectByBeans(Employee employee);

xml:

参数的引用直接使用实体类的字段

<select id="selectByBeans" resultMap="BaseResultMap" parameterType="com.wg.demo.po.Employee">
  select
  *
  from employee where gender = #{gender} and age = #{age}
select>

5. 使用json传递数据

controller:  使用@RequestBody注解之后，前端发送的json数据不会被转化为对象

@ApiOperation(value = "多个参数查询_通过JSON传递多个参数")
@PostMapping("findByJSONObject")
public ResultMsg findByJSONObject(@RequestBody JSONObject params)
{
    List result= employeeMapper.findByJSONObject(params); //
    return ResultMsg.getMsg(result);
}

mapper:

List  findByJSONObject(JSONObject params);

xml:

<select id="findByJSONObject" resultMap="BaseResultMap" parameterType="com.alibaba.fastjson.JSONObject">
  select
  *
  from employee where gender = #{gender} and age = #{age}
select>

6.

传递集合类型参数List、Set、Array

controller：

@ApiOperation(value = "多个参数查询_通过List、Set、Array传递多个参数")
@PostMapping("findByList")
public ResultMsg findByList(@RequestBody List list)
{
    List result= employeeMapper.findByList (list);
    return ResultMsg.getMsg(result);
}

mapper：

List  findByList(List list);

xml：

  <select id="findByList" resultMap="BaseResultMap" >
SELECT * from employee where age in
    <foreach collection="list" open="(" separator="," close=")" item="age">
      #{age}
    foreach>
  select>

foreach元素的属性主要有 item，index，collection，open，separator，close。
item表示集合中每一个元素进行迭代时的别名，
index指定一个名字，用于表示在迭代过程中，每次迭代到的位置，
open表示该语句以什么开始，
separator表示在每次进行迭代之间以什么符号作为分隔符，

close表示以什么结束

在使用foreach的时候最关键的也是最容易出错的就是collection属性，该属性是必须指定的，但是在不同情况下，该属性的值是不一样的，主要有一下3种情况：

1.如果传入的是单参数且参数类型是一个List的时候，collection属性值为list
2.如果传入的是单参数且参数类型是一个array数组的时候，collection的属性值为array
3.如果传入的参数是多个的时候，我们就需要把它们封装成一个Map或者Object

7. 参数类型为对象+集合

pojo：

@Data
public class Department {
    private Long id;

    private String deptName;

    private String descr;

    private Date createTime;

    List employees;

}

controller

@ApiOperation(value = "多个参数查询_对象+集合参数")
@PostMapping("findByDepartment")
public ResultMsg findByDepartment(@RequestBody Department department)
{
    List result= employeeMapper.findByDepartment(department);
    return ResultMsg.getMsg(result);
}

mapper：

List  findByDepartment(@Param("department")Department department);

xml;

<select id="findByDepartment" resultMap="BaseResultMap" parameterType="com.wg.demo.po.Department">
    SELECT * from employee where dept_id =#{department.id} and age in
    <foreach collection="department.employees" open="(" separator="," close=")" item="employee">
        #{employee.age}
    foreach>
select>

请求参数： 查询部门Id=1，并且年龄 等于24和25的员工

{
  "createTime": "2019-07-02T10:17:16.756Z",
  "deptName": "string",
  "descr": "string",
  "employees": [
    {
      "age": "24",
    },
    {
      "age": "25",
    }
  ],
  "id": 1
}

结果：

{
  "data": [
    {
      "address": "北新街ndcpc",
      "age": "24",
      "createTime": 1562062434000,
      "deptId": "1",
      "gender": 1,
      "id": "318397755696631808",
      "name": "kls0bx19cy"
    },
    {
      "address": "北新街lavi0",
      "age": "25",
      "createTime": 1562062436000,
      "deptId": "1",
      "gender": 1,
      "id": "318397755801489408",
      "name": "gj9q3ygikh"
    }
  ],
  "result": "SUCCESS",
  "resultCode": 200,
  "resultMsg": ""
}

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