标签：多个 导入 ddr number string 嵌套 图片 tis param
1 一对一映射
比如每位学生有一个地址。
public class Address
{
private Integer addrId;
private String street;
private String city;
private String state;
private String zip;
private String country;
// setters & getters
}
public class Student
{
private Integer studId;
private String name;
private String email;
private PhoneNumber phone;
private Address address;
//setters & getters
}
我们根据学生 ID 选择学生信息
方法一：使用句点符号表示嵌套对象的引用，
Student 的 address 属性使用了圆点记法被赋上了 address 对应列的值。
View Code
方法二：使用mybatis提供的一对一映射，关键字：association
1）
<resultMap type="Address" id="AddressResult">
<id property="addrId" column="addr_id" />
<result property="street" column="street" />
<result property="city" column="city" />
<result property="state" column="state" />
<result property="zip" column="zip" />
<result property="country" column="country" />
</resultMap>
<resultMap type="Student" id="StudentWithAddressResult">
<id property="studId" column="stud_id" />
<result property="name" column="name" />
<result property="email" column="email" />
<association property="address" resultMap="AddressResult" />
</resultMap>
<select id="findStudentWithAddress" parameterType="int"
resultMap="StudentWithAddressResult">
SELECT STUD_ID, NAME, EMAIL, A.ADDR_ID, STREET, CITY, STATE,
ZIP, COUNTRY
FROM STUDENTS S LEFT OUTER JOIN ADDRESSES A ON
S.ADDR_ID=A.ADDR_ID
WHERE STUD_ID=#{studId}
</select>
元素<association>被用来导入“有一个”(has-one)类型的关联。
如果内嵌的对象有对应的 resultMap 那么使用 <association property="address" resultMap="AddressResult" /> 比较方便。如果内嵌对象需要其它的查询来生成对象，使用方法 3）比较好。
2）也可以使用<association 定义内联的 resultMap，代码如下所示：
<resultMap type="Student" id="StudentWithAddressResult">
<id property="studId" column="stud_id" />
<result property="name" column="name" />
<result property="email" column="email" />
<association property="address" javaType="Address">
<id property="addrId" column="addr_id" />
<result property="street" column="street" />
<result property="city" column="city" />
<result property="state" column="state" />
<result property="zip" column="zip" />
<result property="country" column="country" />
</association>
</resultMap>
3）通过使用嵌套 select 查询来获取 Student 及其 Address 信息，代码如下：
<resultMap type="Address" id="AddressResult">
<id property="addrId" column="addr_id" />
<result property="street" column="street" />
<result property="city" column="city" />
<result property="state" column="state" />
<result property="zip" column="zip" />
<result property="country" column="country" />
</resultMap>
<select id="findAddressById" parameterType="int" resultMap="AddressResult">
SELECT * FROM ADDRESSES WHERE ADDR_ID=#{id}
</select>
<resultMap type="Student" id="StudentWithAddressResult">
<id property="studId" column="stud_id" />
<result property="name" column="name" />
<result property="email" column="email" />
<association property="address" column="addr_id" select="findAddressById" />
</resultMap>
<select id="findStudentWithAddress" parameterType="int" resultMap="StudentWithAddressResult">
SELECT * FROM STUDENTS WHERE STUD_ID=#{Id}
</select>
在此方式中，<association>元素的 select 属性被设置成了 id 为 findAddressById 的语句。这里，两个分开的SQL 语句将会在数据库中执行，第一个调用 findStudentWithAddress 加载 student 信息，而第二个调用 findAddressById 来加载 address 信息。
Addr_id 列的值将会被作为输入参数传递给 selectAddressById 语句；如果有多个参数可以通过逗号分隔。
2 一对多映射，关键词使用 <collection>
比如老师和课程的关系，老师可以讲多门课程，每门课程有一个老师
public class Course
{
private Integer courseId;
private String name;
private String description;
private Date startDate;
private Date endDate;
private Integer tutorId;
//setters & getters
}
public class Tutor
{
private Integer tutorId;
private String name;
private String email;
private Address address;
private List<Course> courses;
// setters & getters
}
1）使用内嵌结果 ResultMap 实现一对多映射。下面是配置文件
<resultMap type="Course" id="CourseResult">
<id column="course_id" property="courseId" />
<result column="name" property="name" />
<result column="description" property="description" />
<result column="start_date" property="startDate" />
<result column="end_date" property="endDate" />
</resultMap>
<resultMap type="Tutor" id="TutorResult">
<id column="tutor_id" property="tutorId" />
<result column="tutor_name" property="name" />
<result column="email" property="email" />
<collection property="courses" resultMap="CourseResult" />
</resultMap>
<select id="findTutorById" parameterType="int" resultMap="TutorResult">
SELECT T.TUTOR_ID, T.NAME AS TUTOR_NAME, EMAIL, C.COURSE_ID,
C.NAME, DESCRIPTION, START_DATE, END_DATE
FROM TUTORS T LEFT OUTER JOIN ADDRESSES A ON T.ADDR_ID=A.ADDR_ID
LEFT OUTER JOIN COURSES C ON T.TUTOR_ID=C.TUTOR_ID
WHERE T.TUTOR_ID=#{tutorId}
</select>
<collection>元素的 resultMap 属性设置成了 CourseResult，CourseResult 包含了 Course 对象属性与表列名之间的映射。
2）使用嵌套 Select 语句实现一对多映射，配置文件如下
<resultMap type="Course" id="CourseResult">
<id column="course_id" property="courseId" />
<result column="name" property="name" />
<result column="description" property="description" />
<result column="start_date" property="startDate" />
<result column="end_date" property="endDate" />
</resultMap>
标签：多个 导入 ddr number string 嵌套 图片 tis param
原文地址：http://www.cnblogs.com/www123----/p/7857354.html
