MyBatis最常用之返回结果映射方法

惯例:先生成实体类.

 

岗位实体类:

package cn.xxx.entity;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

public class Post implements Serializable{
    private static final long serialVersionUID = 8958411428421018244L;
    
    private Long postId;
    private String postContent;
    private Long postTime;
    //private Long personId;
    private Person person;
    private List<Comment> comments = new ArrayList<Comment>();
    
    public Post() {
    }

    public Post(Long postId, String postContent, Long postTime, Person person, List<Comment> comments) {
        super();
        this.postId = postId;
        this.postContent = postContent;
        this.postTime = postTime;
        this.person = person;
        this.comments = comments;
    }

    public Long getPostId() {
        return postId;
    }

    public void setPostId(Long postId) {
        this.postId = postId;
    }

    public String getPostContent() {
        return postContent;
    }

    public void setPostContent(String postContent) {
        this.postContent = postContent;
    }

    public Long getPostTime() {
        return postTime;
    }

    public void setPostTime(Long postTime) {
        this.postTime = postTime;
    }

    public Person getPerson() {
        return person;
    }

    public void setPerson(Person person) {
        this.person = person;
    }

    public List<Comment> getComments() {
        return comments;
    }

    public void setComments(List<Comment> comments) {
        this.comments = comments;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((comments == null) ? 0 : comments.hashCode());
        result = prime * result + ((person == null) ? 0 : person.hashCode());
        result = prime * result + ((postContent == null) ? 0 : postContent.hashCode());
        result = prime * result + ((postId == null) ? 0 : postId.hashCode());
        result = prime * result + ((postTime == null) ? 0 : postTime.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Post other = (Post) obj;
        if (comments == null) {
            if (other.comments != null)
                return false;
        } else if (!comments.equals(other.comments))
            return false;
        if (person == null) {
            if (other.person != null)
                return false;
        } else if (!person.equals(other.person))
            return false;
        if (postContent == null) {
            if (other.postContent != null)
                return false;
        } else if (!postContent.equals(other.postContent))
            return false;
        if (postId == null) {
            if (other.postId != null)
                return false;
        } else if (!postId.equals(other.postId))
            return false;
        if (postTime == null) {
            if (other.postTime != null)
                return false;
        } else if (!postTime.equals(other.postTime))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Post [postId=" + postId + ", postContent=" + postContent + ", postTime=" + postTime + ", person="
                + person + ", comments=" + comments + "]";
    }
    
}

 

人员实体类:

package cn.xxx.entity;

import java.io.Serializable;

public class Person implements Serializable{
    private static final long serialVersionUID = 2125601210807098412L;
    
    private Long personId;
    private String personName;
    private int personAge;
    
    public Person() {
    }

    public Person(Long personId, String personName, int personAge) {
        super();
        this.personId = personId;
        this.personName = personName;
        this.personAge = personAge;
    }

    public Long getPersonId() {
        return personId;
    }

    public void setPersonId(Long personId) {
        this.personId = personId;
    }

    public String getPersonName() {
        return personName;
    }

    public void setPersonName(String personName) {
        this.personName = personName;
    }

    public int getPersonAge() {
        return personAge;
    }

    public void setPersonAge(int personAge) {
        this.personAge = personAge;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + personAge;
        result = prime * result + ((personId == null) ? 0 : personId.hashCode());
        result = prime * result + ((personName == null) ? 0 : personName.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Person other = (Person) obj;
        if (personAge != other.personAge)
            return false;
        if (personId == null) {
            if (other.personId != null)
                return false;
        } else if (!personId.equals(other.personId))
            return false;
        if (personName == null) {
            if (other.personName != null)
                return false;
        } else if (!personName.equals(other.personName))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Person [personId=" + personId + ", personName=" + personName + ", personAge=" + personAge + "]";
    }

}

 

评价实体类:

package cn.xxx.entity;

import java.io.Serializable;

public class Comment implements Serializable{
    private static final long serialVersionUID = 9005740179566619541L;
    
    private Long commentId;
    private String content;
    
    public Comment() {
    }
    
    public Comment(Long commentId, String content) {
        super();
        this.commentId = commentId;
        this.content = content;
    }

    public Long getCommentId() {
        return commentId;
    }

    public void setCommentId(Long commentId) {
        this.commentId = commentId;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((commentId == null) ? 0 : commentId.hashCode());
        result = prime * result + ((content == null) ? 0 : content.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Comment other = (Comment) obj;
        if (commentId == null) {
            if (other.commentId != null)
                return false;
        } else if (!commentId.equals(other.commentId))
            return false;
        if (content == null) {
            if (other.content != null)
                return false;
        } else if (!content.equals(other.content))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Comment [commentId=" + commentId + ", content=" + content + "]";
    }
    
}

 

mapper接口:

package cn.xxx.mapper;

import cn.xxx.entity.Post;

public interface PostMapper {
    
    Post findPostByPostId(Long postId);
    
}

 

mapper实现:

<?xml version="1.0" encoding="UTF-8" ?>  
<!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"      
 "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">

<mapper namespace="cn.xxx.mapper.PostMapper">

    <select id="findPostByPostId" parameterType="long" resultMap="rMap">
        select 
            po.post_id as postId,
            po.post_content as postContent,
            po.post_time as postTime,
            pe.person_id as personId,
            pe.person_name as personName,
            pe.person_age as personAge
        from
            post po
        left join
            person pe
        on 
            po.person_id=pe.person_id
        where 
            po.post_id=#{postId}
    </select>


    <resultMap id="rMap" type="cn.xxx.entity.Post">
        
        <!-- id代表实体主键 -->
        <!-- property对应实体类属性, column是DB字段,如果改名了必须取改名后的 -->
        <id property="postId" column="postId"/>
        <result property="postContent" column="postContent"/>
        <result property="postTime" column="postTime"/>
        
        <!-- association 映射关联查询(单例) -->
        <!-- association property是本实体类中的字段属性名, javaType声明对应什么类型 -->
        <association property="person" javaType="cn.xxx.entity.Person">
            <!-- id代表实体主键 -->
            <!-- property对应实体类属性, column是DB字段,如果改名了必须取改名后的 -->
            <id property="personId" column="personId"/>
            <result property="personName" column="personName"/>
            <result property="personAge" column="personAge"/> 
        </association>
        
        <!-- collection 映射集合(多例), 需要传入column DB字段,如果改名了必须取改名后的 -->
        <collection property="comments" select="findCommentsByPostId" column="postId"/>
        
    </resultMap>
    
    
    <select id="findCommentsByPostId" resultType="cn.xxx.entity.Comment">
        select
            comment_id as commentId,
            content as content
        from
            comment
        where
            post_id=#{postId}
    </select>
    
</mapper>

 

进行测试:

 

测试方法:

    @Test
    public void testFindPostByPostId(){
        PostMapper postMapper = ctx.getBean("postMapper", PostMapper.class);
        Post post = postMapper.findPostByPostId(1L);
        System.out.println(post);
    }

 

打印结果:

Post [postId=1, postContent=开发, postTime=9, person=Person [personId=2, personName=jack, personAge=23], comments=[Comment [commentId=1, content=gfhgfjhgj], Comment [commentId=2, content=fgdgdfg], Comment [commentId=3, content=fdgdfgdfg]]]

 

 

转发请注明: 转自http://www.cnblogs.com/gscq073240/articles/6905306.html