mybatis——动态sql、where、if、foreach（四）

(一）if 和 where

<!--where会自动处理if标签里面的第一个and不会处理之后if里的and-->
<select id="queryPersonBySexName" resultType="Person" parameterType="Person">
  select id,name,sex from person
  <where>
      <if test="name!=null and name!=''">
          and name = #{name}
      </if>
      <if test="sex!=null">
          and  sex = #{sex,javaType=boolean , jdbcType = VARCHAR}
      </if>
  </where>

</select>

测试方法：

/*通过if语句来传参*/
Person person = new Person();
person.setSex(true);
person.setName("陈勇丞");
Person person1 = mapper.queryPersonBySexName(person);
System.out.println(person1);

（二）列表循环查询

<--循环查询 列表查询 separator分隔符-->
<select id="queryPersonForById" parameterType="java.util.List" resultType="Person">
    select * from person
    <where>
        <if test="list!=null and list.size>0">
          <foreach collection="list" open=" and id in(" close=")" item="id" separator=",">
              #{id}
          </foreach>
        </if>
    </where>
</select>

测试方法：

/*列表循环查询*/
List<Integer> List = new ArrayList<>();
List.add(1);
List.add(2);
List.add(5);
List<Person> list1 = mapper.queryPersonForById(List);
System.out.println(list1);

（三）简单数组查询

<!--循环 简单数组查询 要用array来代替-->
<select id="queryPersonForById" parameterType="int[]" resultType="Person">
    select * from person
    <where>
        <if test="array!=null and array.length">
            <foreach collection="array" open=" and id in(" close=")" item="id" separator=",">
                #{id}
            </foreach>
        </if>
    </where>
</select>

测试方法：

/*简单数组循环查询*/
int []a={1,2,5};
List<Person> people = mapper.queryPersonForById(a);
System.out.println(people);

(四) 对象数组

<!--循环 对象数组 parameterType="Object[]" item="对象名"-->
<select id="queryPersonForById" parameterType="Object[]" resultType="Person">
    select * from person
    /*导入sql如果在其他的包 需要先在config加载 在用命名空间.sql的id*/
    <include refid="com.xiaonuo.Interface.abc.queryByIdPersonArray" />
</select>

测试方法：

/*对象数组循环查询*/
Person person1 = new Person();
person1.setId(1L);
Person person2 = new Person();
person2.setId(2L);
Person person3 = new Person();
person3.setId(5L);
Person []persons = {person1,person2,person3};
List<Person> people = mapper.queryPersonForById(persons);
System.out.println(people);

(五)map查询

<!--循环 map collection取的是键名-->
    <select id="queryPersonForById" parameterType="java.util.HashMap" resultType="Person">
        select * from person
        <where>
            <if test="list!=null">
                <foreach collection="list"  open=" and id in(" close=")" item="item" separator=",">
                    #{item.id}
                </foreach>
            </if>
        </where>
    </select>

测试方法：

/*map查询*/
Person person1 = new Person();
person1.setId(1L);
Person person2 = new Person();
person2.setId(2L);
Person person3 = new Person();
person3.setId(5L);
List<Person> list1 = new ArrayList<>();
list1.add(person1);
list1.add(person2);
list1.add(person3);
Map map = new HashMap();
map.put("list",list1);
List<Person> people = mapper.queryPersonForById(map);
System.out.println(people);