MyBatis使用select关联 一对多表的时候？？？？？？？？？？？？？
SchoolMapper.xml 关联关系是一个学校里面有很多学生
student 表的属性如下:
school表如下：
school.xml如下:
public class School {
//建立一对多的关系
private List<Student> slist;
public List<Student> getSlist() {
return slist;
}
public void setSlist(List<Student> slist) {
this.slist = slist;
}
private Integer sId;
private String sName;
private String sAddress;
public Integer getsId() {
return sId;
}
public void setsId(Integer sId) {
this.sId = sId;
}
public String getsName() {
return sName;
}
public void setsName(String sName) {
this.sName = sName == null ? null : sName.trim();
}
public String getsAddress() {
return sAddress;
}
public void setsAddress(String sAddress) {
this.sAddress = sAddress == null ? null : sAddress.trim();
}
public class Student {
//建立多多对一的关系
private School school;
public School getSchool() {
return school;
}
public void setSchool(School school) {
this.school = school;
}
private Integer stId;
private String stClass;
private String stName;
private String stDream;
private Integer stS;
public Integer getStId() {
return stId;
}
public void setStId(Integer stId) {
this.stId = stId;
}
public String getStClass() {
return stClass;
}
public void setStClass(String stClass) {
this.stClass = stClass == null ? null : stClass.trim();
}
public String getStName() {
return stName;
}
public void setStName(String stName) {
this.stName = stName == null ? null : stName.trim();
}
public String getStDream() {
return stDream;
}
public void setStDream(String stDream) {
this.stDream = stDream == null ? null : stDream.trim();
}
public Integer getStS() {
return stS;
}
public void setStS(Integer stS) {
this.stS = stS;
}
test.java 结果list就是null
public static void main(String[] args) {
// TODO Auto-generated method stub
StuService ss=new StuService();
ss.selectSchool();
}
public void selectSchool(){
SqlSession ss=null;
try {
ss=sf.openSession();
//selectByPrimaryKey
School sc =ss.selectOne("com.wuye.dao.SchoolMapper.selectSchool", 1);
System.out.println("学校的信息:"+sc.getsId()+" "+sc.getsName()+" "+sc.getsAddress());
List<Student> lis=sc.getSlist();
for(Student st:lis){
System.out.println("学生信息学号:"+st.getStId()+"名字:"+st.getStName()+"所在班级: "+st.getStClass()+"梦想:"+st.getStDream()+"所在学校编号:=="+st.getStS());
}
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
## # 上面肯写的不清楚：
SchoolMapper.xml 关联关系是一个学校里面有很多学生
<select id="selectSchool" resultMap="BaseResultMap3" parameterType="java.lang.Integer">
select * from school sc where sc.s_id=#{sId,jdbcType=INTEGER}
</collection>
select st_id stId, st_class stClass, st_name stName,st_dream stDream
from student s where s.st_s=#{sId,jdbcType=INTEGER}
StudentMapper.xml
<mapper namespace="com.wuye.dao.StudentMapper" >
<association property="school" column="st_s" select="selectShoolByStu" ></association>
两个表：!
public class School {
//建立一对多的关系
private List<Student> slist;
public List<Student> getSlist() {
return slist;
}
public void setSlist(List<Student> slist) {
this.slist = slist;
}
private Integer sId;
private String sName;
private String sAddress;
public Integer getsId() {
return sId;
}
public void setsId(Integer sId) {
this.sId = sId;
}
public String getsName() {
return sName;
}
public void setsName(String sName) {
this.sName = sName == null ? null : sName.trim();
}
public String getsAddress() {
return sAddress;
}
public void setsAddress(String sAddress) {
this.sAddress = sAddress == null ? null : sAddress.trim();
}
public class Student {
//建立多多对一的关系
private School school;
public School getSchool() {
return school;
}
public void setSchool(School school) {
this.school = school;
}
private Integer stId;
private String stClass;
private String stName;
private String stDream;
private Integer stS;
public Integer getStId() {
return stId;
}
public void setStId(Integer stId) {
this.stId = stId;
}
public String getStClass() {
return stClass;
}
public void setStClass(String stClass) {
this.stClass = stClass == null ? null : stClass.trim();
}
public String getStName() {
return stName;
}
public void setStName(String stName) {
this.stName = stName == null ? null : stName.trim();
}
public String getStDream() {
return stDream;
}
public void setStDream(String stDream) {
this.stDream = stDream == null ? null : stDream.trim();
}
public Integer getStS() {
return stS;
}
public void setStS(Integer stS) {
this.stS = stS;
}
test.java 结果list就是null
public static void main(String[] args) {
// TODO Auto-generated method stub
StuService ss=new StuService();
ss.selectSchool();
}
public void selectSchool(){
SqlSession ss=null;
try {
ss=sf.openSession();
//selectByPrimaryKey
School sc =ss.selectOne("com.wuye.dao.SchoolMapper.selectSchool", 1);
System.out.println("学校的信息:"+sc.getsId()+" "+sc.getsName()+" "+sc.getsAddress());
List<Student> lis=sc.getSlist();
for(Student st:lis){
System.out.println("学生信息学号:"+st.getStId()+"名字:"+st.getStName()+"所在班级: "+st.getStClass()+"梦想:"+st.getStDream()+"所在学校编号:=="+st.getStS());
}
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
是这样的啊，定义自己定义resultMap指定类的属性和查询列的映射关系，集合列指定select语句。
你这段代码怎么了，有报错么？