MyBatis浅尝笔记

Posted 2020-08-28 吕亚辉的博客

MyBatis应属于一种轻量级的java持久层技术，它通过简单的SQL xml或注解，将数据库数据映射到接口与POJO。最近项目要用到mybatis，所以学习之后在这里做个总结，文中的示例以xml配置为主，mybatis也支持注解的方式。

测试数据

先给出demo所使用的表结构，以典型的用户（1）-文章（n）的关系表做demo数据

 1 #
 2 # mysql数据库：数据库名 :dblog
 3 #
 4 
 5 DROP TABLE IF EXISTS m_category;
 6 CREATE TABLE m_category (
 7   id int(11) NOT NULL AUTO_INCREMENT,
 8   name varchar(64) NOT NULL COMMENT \'分类名称\',
 9   parent_id INT NOT NULL ,
10   level INT NOT NULL DEFAULT 0,
11   path VARCHAR(64) NOT NULL COMMENT \'栏目路径，rootId-xxId-xxId\',
12   PRIMARY KEY (id)
13 ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
14 
15 DROP TABLE IF EXISTS m_post;
16 CREATE TABLE m_post (
17   id int(11) NOT NULL AUTO_INCREMENT,
18   category_id INT NOT NULL ,
19   user_id INT NOT NULL ,
20   title varchar(64) NOT NULL COMMENT \'标题\',
21   content text COMMENT \'正文\',
22   created_at timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
23   updated_at timestamp NOT NULL DEFAULT \'0000-00-00 00:00:00\',
24   PRIMARY KEY (id)
25 ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
26 
27 DROP TABLE IF EXISTS m_user;
28 CREATE TABLE m_user (
29   id int(11) NOT NULL AUTO_INCREMENT,
30   username varchar(64) NOT NULL,
31   password varchar(255) NOT NULL,
32   salt VARCHAR(32) NOT NULL ,
33   avatar varchar(64) DEFAULT NULL,
34   type enum(\'customer\',\'admin\',\'root\') NOT NULL DEFAULT \'customer\',
35   remember_token varchar(128) DEFAULT NULL,
36   PRIMARY KEY (id)
37 ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
38 
39 INSERT INTO m_user(id,username, password, salt,type)
40     VALUE (1,\'lvyahui\',\'XXXXXXX\',\'abcs\',\'admin\');
41 
42 DROP TABLE IF EXISTS m_post_comment;
43 CREATE TABLE m_post_comment(
44   id int(11) AUTO_INCREMENT PRIMARY KEY ,
45   post_id INT NOT NULL ,
46   user_id INT NOT NULL ,
47   content VARCHAR(512) NOT NULL DEFAULT \'\',
48   created_at TIMESTAMP NOT NULL DEFAULT current_timestamp,
49   updated_at TIMESTAMP NOT NULL DEFAULT \'0000-00-00 00:00:00\'
50 ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

对应的实体类

Post

 1 package org.lyh.java.mybatis.model;
 2 
 3 import java.sql.Timestamp;
 4 
 5 /**
 6  * @author lvyahui ([e-mail],[e-mail])
 7  * @since 2017/1/1 14:00
 8  */
 9 @SuppressWarnings("unused")
10 public class Post extends BaseModel {
11 
12     private String title;
13     private String content;
14     private Timestamp createdAt;
15     private Timestamp updatedAt;
16 
17     private Integer userId;
18     private Integer categoryId;
19 
20     private User user;
21     private Category category;
22 
23     public String getTitle() {
24         return title;
25     }
26 
27     public void setTitle(String title) {
28         this.title = title;
29     }
30 
31     public String getContent() {
32         return content;
33     }
34 
35     public void setContent(String content) {
36         this.content = content;
37     }
38 
39     public Timestamp getCreatedAt() {
40         return createdAt;
41     }
42 
43     public void setCreatedAt(Timestamp createdAt) {
44         this.createdAt = createdAt;
45     }
46 
47     public Timestamp getUpdatedAt() {
48         return updatedAt;
49     }
50 
51     public void setUpdatedAt(Timestamp updatedAt) {
52         this.updatedAt = updatedAt;
53     }
54 
55     public Integer getUserId() {
56         return userId;
57     }
58 
59     public void setUserId(Integer userId) {
60         this.userId = userId;
61     }
62 
63     public Integer getCategoryId() {
64         return categoryId;
65     }
66 
67     public void setCategoryId(Integer categoryId) {
68         this.categoryId = categoryId;
69     }
70 
71     public User getUser() {
72         return user;
73     }
74 
75     public void setUser(User user) {
76         this.user = user;
77     }
78 
79     public Category getCategory() {
80         return category;
81     }
82 
83     public void setCategory(Category category) {
84         this.category = category;
85     }
86 
87 
88     @Override
89     public String toString() {
90         return "Post{" +
91                 "title=\'" + title + \'\\\'\' +
92                 ", content=\'" + content + \'\\\'\' +
93                 ", createdAt=" + createdAt +
94                 ", updatedAt=" + updatedAt +
95                 ", userId=" + userId +
96                 ", categoryId=" + categoryId +
97                 \'}\';
98     }
99 }

lvyahui

User

 1 package org.lyh.java.mybatis.model;
 2 
 3 import org.lyh.java.mybatis.type.UserType;
 4 
 5 import java.util.List;
 6 
 7 /**
 8  * @author lvyahui ([e-mail],[e-mail])
 9  * @since 2017/1/12 22:44
10  */
11 @SuppressWarnings("unused")
12 public class User extends BaseModel {
13 
14 
15     private String username;
16     private String password;
17     private String salt;
18     private String avatar;
19     private UserType type;
20     private String rememberToken;
21 
22     private List<Post> posts ;
23     private List<PostComment> postComments;
24 
25     public String getUsername() {
26         return username;
27     }
28 
29     public void setUsername(String username) {
30         this.username = username;
31     }
32 
33     public String getPassword() {
34         return password;
35     }
36 
37     public void setPassword(String password) {
38         this.password = password;
39     }
40 
41     public String getSalt() {
42         return salt;
43     }
44 
45     public void setSalt(String salt) {
46         this.salt = salt;
47     }
48 
49     public String getAvatar() {
50         return avatar;
51     }
52 
53     public void setAvatar(String avatar) {
54         this.avatar = avatar;
55     }
56 
57     public UserType getType() {
58         return type;
59     }
60 
61     public void setType(UserType type) {
62         this.type = type;
63     }
64 
65     public String getRememberToken() {
66         return rememberToken;
67     }
68 
69     public void setRememberToken(String rememberToken) {
70         this.rememberToken = rememberToken;
71     }
72 
73     public List<Post> getPosts() {
74         return posts;
75     }
76 
77     public void setPosts(List<Post> posts) {
78         this.posts = posts;
79     }
80 
81     public List<PostComment> getPostComments() {
82         return postComments;
83     }
84 
85     public void setPostComments(List<PostComment> postComments) {
86         this.postComments = postComments;
87     }
88 }

lvyahui

一些辅助类

查询条件Condition

 1 package org.lyh.java.mybatis.bean;
 2 
 3 /**
 4  * @author lvyahui ([e-mail],[e-mail])
 5  * @since 2016/12/12 13:27
 6  */
 7 @SuppressWarnings("unused")
 8 public class Condition {
 9 
10     private String key;
11     private String opt = "=";
12     private Object value;
13 
14     public Condition(String key, String opt, Object value) {
15         this.key = key;
16         this.opt = opt;
17         this.value = value;
18     }
19 
20     public Condition(String key, Object value){
21         this(key,"=",value);
22     }
23 
24     public String getKey() {
25         return key;
26     }
27 
28     public void setKey(String key) {
29         this.key = key;
30     }
31 
32     public String getOpt() {
33         return opt;
34     }
35 
36     public void setOpt(String opt) {
37         this.opt = opt;
38     }
39 
40     public Object getValue() {
41         return value;
42     }
43 
44     public void setValue(Object value) {
45         this.value = value;
46     }
47 }

lvyahui

分页工具类PageData

  1 package org.lyh.java.mybatis.bean;
  2 
  3 
  4 import org.lyh.java.mybatis.model.BaseModel;
  5 
  6 import java.util.List;
  7 
  8 /**
  9  *
 10  * Created by lvyahui on 2015/7/12.
 11  */
 12 @SuppressWarnings("unused")
 13 public class PageData<T extends BaseModel> {
 14 
 15     /**
 16      * 前端做分页，所以这里limit设置的非常大，相当于不分页
 17      */
 18     public static final int DEFAULT_SIZE = 1000;
 19 
 20     private List<T> datas;
 21 
 22     private int currentPage = 1;
 23 
 24     private int totalPage;
 25 
 26     private int totalItem;
 27 
 28 
 29     private int maxBtnCount = 10;
 30 
 31     private int pageSize = DEFAULT_SIZE;
 32 
 33     private int start = 1;
 34     private int end;
 35 
 36     /**
 37      * 总项目数
 38      */
 39     public int getTotalItem() {
 40         return totalItem;
 41     }
 42 
 43     public void setTotalItem(int totalItem) {
 44         this.totalItem = totalItem;
 45         paging();
 46     }
 47 
 48     private void paging() {
 49         totalPage = totalItem / pageSize + 1;
 50         if(totalPage > maxBtnCount){
 51             if(currentPage <= (maxBtnCount-1)/2){
 52                 // 靠近首页
 53                 start = 1;
 54             }else if(totalPage-currentPage < (maxBtnCount-1)/2){
 55                 // 靠近尾页
 56                 start = totalPage - maxBtnCount - 1;
 57             }else{
 58                 start = currentPage - (maxBtnCount-1)/2;
 59             }
 60             end = maxBtnCount-1 + start > totalPage ? totalPage : maxBtnCount - 1 + start;
 61         }else{
 62             end = totalPage;
 63         }
 64 //        System.out.println("start:"+start+",end:"+end);
 65     }
 66 
 67     /**
 68      * 总页数
 69      */
 70     public int getTotalPage() {
 71         return totalPage;
 72     }
 73 
 74     /**
 75      * 当前页
 76      */
 77     public int getCurrentPage() {
 78         return currentPage;
 79     }
 80 
 81     public void setCurrentPage(int currentPage) {
 82         this.currentPage = currentPage;
 83     }
 84 
 85     /**
 86      * 页面数据
 87      */
 88     public List<T> getDatas() {
 89         return datas;
 90     }
 91 
 92     public void setDatas(List<T> datas) {
 93         this.datas = datas;
 94     }
 95 
 96     /**
 97      * 每页大小，可放多少个项，默认为10
 98      */
 99 
100 
101     public int getPageSize() {
102         return pageSize;
103     }
104 
105     public void setPageSize(int pageSize) {
106         this.pageSize = pageSize;
107     }
108 
109     /**
110      * @return 最大分页按钮数，默认值为10
111      */
112     public int getMaxBtnCount() {
113         return maxBtnCount;
114     }
115 
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