Mybatis Learning-4

Category and article bidirectional one-to-many association

(1) Implementation of the CategoryDao

public class Categorydaoimpl extends basedao<category> implements CategoryDao {

@Override

public boolean addcategory (category category) {

try {

Super.add (category);

return true;

} catch (Exception e) {

E.printstacktrace ();

return false;

}

}

@Override

Public Category Getcategorybyid (int id) {

return Super.getbyid (ID);

}

@Override

Public list<category> Getallcategorys () {

return Super.getall ();

}

}

(2) Implementation of the Articledao

public class Articledaoimpl extends basedao<article> implements Articledao {

@Override

public Boolean addarticle (article article) {

try {

Super.add (article);

return true;

} catch (Exception e) {

E.printstacktrace ();

return false;

}

}

@Override

Public article Getarticlebyid (int id) {

return Super.getbyid (ID);

}

@Override

Public list<article> Getallarticles () {

return Super.getall ();

}

@Override

Public list<article> getarticelsbycategory (int categoryId) {

map<string,object> params = new hashmap<string,object> ();

Params.put ("CID", categoryId);

Return Super.getlist ("Selectbycategory", params);

}

@Override

Public list<article> Getarticlesbytitle (String title) {

map<string,object> params = new hashmap<string,object> ();

Params.put ("title", title);

Return Super.getlist ("Selectbytitle", params);

}

}

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Because article has a many-to-one association with user and category, foreign key additions can be problematic when adding data

Therefore, before making the mapping file, the article entity class is modified to add the corresponding attribute of the table foreign key column to the entity class.

Many-to-one references

Private category category;

private int Cateid;

Many-to-one references

private user user;

private int userId;

-------Note the above modification of the entity class, adding two foreign key-based property settings (Userid,cateid)

public void Setcategory (category category) {

　This.setcateid (Category.getid ());

this.category = category;

}

public void SetUser (user user) {

　This.setuserid (User.getid ());

This.user = user;

}

--------------Note that the above code is modified to add two original property set methods to the red code

======================================

(3) Category mapping file

<?xml version= "1.0" encoding= "UTF-8"?>

<! DOCTYPE Mapper Public "-//mybatis.org//dtd mapper 3.0//en"

"Http://mybatis.org/dtd/mybatis-3-mapper.dtd" >

<mapper namespace= "Cn.smartapp.blogs.pojo.Category" >

<resultmap type= "Category" id= "Categoryresult" >

<id column= "CID" property= "id"/>

<result column= "Cate_name" property= "Catename"/>

<!--a one-to-many association settings-

<collection property= "Articels" oftype= "article" javatype= "Java.util.Set" >

<id column= "aid" property= "id"/>

<result column= "Art_title" property= "title"/>

<result column= "art_content" property= "content"/>

<result column= "Art_pubtime" property= "Pubtime" javatype= "Java.util.Date"/>

</collection>

</resultMap>

<insert id= "Insertpojo" parametertype= "Category" usegeneratedkeys= "true" >

Insert into Blog_category (cate_name) VALUES (#{catename})

</insert>

<select id= "Selectbyid" resultmap= "Categoryresult" parametertype= "int" >

Select

Tc.id as CID,

Tc.cate_name,

Ta.id as aid,

Ta.art_title,

Ta.art_content,

Ta.art_pubtime,

TA.PUB_USER_ID,

ta.cate_id

From Blog_category as TC inner join blog_article as Ta

On tc.id=ta.cate_id

Where Tc.id=#{id}

</select>

<select id= "SelectAll" resultmap= "Categoryresult" >

Select

Tc.id as CID,

Tc.cate_name,

Ta.id as aid,

Ta.art_title,

Ta.art_content,

Ta.art_pubtime,

TA.PUB_USER_ID,

ta.cate_id

From Blog_category as TC inner join blog_article as Ta

On tc.id=ta.cate_id

</select>

</mapper>

(4) Article mapping file

<?xml version= "1.0" encoding= "UTF-8"?>

<! DOCTYPE Mapper Public "-//mybatis.org//dtd mapper 3.0//en"

"Http://mybatis.org/dtd/mybatis-3-mapper.dtd" >

<mapper namespace= "Cn.smartapp.blogs.pojo.Article" >

<resultmap type= "article" id= "Articleresult" >

<id column= "aid" property= "id"/>

<result column= "Art_title" property= "title"/>

<result column= "art_content" property= "content"/>

<result column= "Art_pubtime" property= "Pubtime" javatype= "Java.util.Date"/>

<!--Many-to-one settings (article and user)-

<association property= "User" foreigncolumn= "pub_user_id" >

<id column= "UID" property= "id"/>

<result column= "user_name" property= "UserName"/>

<result column= "User_pass" property= "password"/>

<result column= "Nick_name" property= "nickname"/>

</association>

<!--Many-to-one settings (article and category)--

<association property= "Category" foreigncolumn= "cate_id" >

<id column= "CID" property= "id"/>

<result column= "Cate_name" property= "Catename"/>

</association>

</resultMap>

<insert id= "Insertpojo" parametertype= "article" usegeneratedkeys= "true" >

Insert into Blog_article (art_title,art_content,art_pubtime,pub_user_id,cate_id)

VALUES (#{title},#{content},#{pubtime},#{userid},#{cateid})

<selectkey >

</selectKey>

</insert>

<select id= "Selectbyid" resultmap= "Articleresult" parametertype= "int" >

Select

Ta.id as aid,

Ta.art_title,

Ta.art_content,

Ta.art_pubtime,

TA.PUB_USER_ID,

TA.CATE_ID,

Tu.id as UID,

Tu.user_name,

Tu.user_pass,

Tu.nick_name,

Tc.id as CID,

Tc.cate_name

From Blog_user as Tu inner joins blog_article as TA on tu.id=ta.pub_user_id

INNER JOIN Blog_category as TC on tc.id=ta.cate_id where Ta.id=#{id}

</select>

<select id= "SelectAll" resultmap= "Articleresult" >

Select

Ta.id as aid,

Ta.art_title,

Ta.art_content,

Ta.art_pubtime,

TA.PUB_USER_ID,

TA.CATE_ID,

Tu.id as UID,

Tu.user_name,

Tu.user_pass,

Tu.nick_name,

Tc.id as CID,

Tc.cate_name

From Blog_user as Tu inner joins blog_article as TA on tu.id=ta.pub_user_id

INNER JOIN Blog_category as TC on TC.ID=TA.CATE_ID

</select>

<select id= "Selectbycategory" resultmap= "Articleresult" >

Select

Ta.id as aid,

Ta.art_title,

Ta.art_content,

Ta.art_pubtime,

TA.PUB_USER_ID,

TA.CATE_ID,

Tu.id as UID,

Tu.user_name,

Tu.user_pass,

Tu.nick_name,

Tc.id as CID,

Tc.cate_name

From Blog_user as Tu inner joins blog_article as TA on tu.id=ta.pub_user_id

INNER JOIN Blog_category as TC on tc.id=ta.cate_id where Tc.id=#{cid}

</select>

<select id= "Selectbytitle" resultmap= "Articleresult" >

Select

Ta.id as aid,

Ta.art_title,

Ta.art_content,

Ta.art_pubtime,

TA.PUB_USER_ID,

TA.CATE_ID,

Tu.id as UID,

Tu.user_name,

Tu.user_pass,

Tu.nick_name,

Tc.id as CID,

Tc.cate_name

From Blog_user as Tu inner joins blog_article as TA on tu.id=ta.pub_user_id

INNER JOIN Blog_category as TC on tc.id=ta.cate_id where ta.title like #{title}

</select>

</mapper>

=========================

(5) Test Article Cascade add operation

public class Articledaoaddtest {

@Test

public void Test () {

Articledao Articledao = new Articledaoimpl ();

CategoryDao CategoryDao = new Categorydaoimpl ();

Article Article = new article (); Create a new article object that will be added

Article.settitle ("Today is a good day to write Java code!")  "); Specify title

Calendar calendar = calendar.getinstance ();//Create Date Object

Article.setpubtime (Calendar.gettime ());//Set the publish time to the current time

Category category = Categorydao.getcategorybyid (1); Query a specified category

article.setcategory (category); Sets the specified classification to the article object (specifies the classification for the article)

User user = new user (); Create a user

User.setid (4); Specifies that the user is a user with an ID of 4 in the database table

article.setuser (user); Specify the publishing user for the article

article.setcontent ("haha haha ...  "); Set the content of an article

Boolean doflag = articledao.addarticle (article); Add an article

assert.asserttrue (doflag);

}

(6) test the category and article one-to-many correlation is useful

public class Categorydaoselecttest {

@Test

public void Test () {

CategoryDao CategoryDao = new Categorydaoimpl ();

Category category = Categorydao.getcategorybyid (1);

int articlecount = Category.getarticels (). Size ();

Because of the correlation, a category contains multiple articles (article)

For (article Article:category.getArticels ()) {

System.out.println (Article.gettitle ());

}

Assert.assertequals (Articlecount, 5);

}

}

Mybatis Learning-4