MyBatis：动态sql（狂神）

 

 

 

 

 

用where标签替代where 1=1，防止出错

 

 

 

 

 

db.properties：

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=&useUnicode=true&characterEncoding=utf-8
username=root
password=123456

mybatis-config.xml：

 Blog：

package com.kuang.pojo;

import lombok.Data;

import java.util.Date;
@Data
public class Blog {
    private String id;
    private String title;
    private String author;
    private Date createTime;//属性名和字段名不一致
    private int views;
}

MybatisUtils：

package com.kuang.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

//sqlSessionFactory --sqlSession
public class MybaitsUtils {
    private static SqlSessionFactory sqlSessionFactory;//提升作用域
    /*
    所谓的代码块就是一段独立的代码空间，那什么是静态代码块呢？说白了，静态代码块就是用static修饰的代码块，关于静态代码块的概念不多说，不过你需要知道它的一个特点，那就是

   随着类的加载而执行，而且只执行一次
     */
    static{
        try {
            //使用MyBaits获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        }catch(IOException e){
            e.printStackTrace();
        }
    }
    //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
    // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。
    public static SqlSession getSqlSession(){
        //获取SqlSession对象
         SqlSession sqlSession=sqlSessionFactory.openSession(true);//true设置事务自动提交，执行增删改，sql不用手动提交
         return sqlSession;
    }
}

IDUtils：生成id

package com.kuang.utils;

import org.junit.Test;

import java.util.UUID;

public class IDUtils {
    public static String getId(){
        return UUID.randomUUID().toString().replaceAll("-","");
    }
    @Test
    public void test(){
        System.out.println(IDUtils.getId());
        System.out.println(IDUtils.getId());
        System.out.println(IDUtils.getId());
    }
}

BlogMapper:

package com.kuang.dao;

import com.kuang.pojo.Blog;

import java.util.List;
import java.util.Map;

public interface BlogMapper {
    //插入数据
    int addBlog(Blog blog);

    //查询博客
    List queryBlogIF(Map map);
}

BlogMapper.xml:动态sql if标签
 

    

    

        insert into mybatis.blog (id, title, author, create_time, views)
        values (#{id},#{title},#{author},#{createTime},#{views});

    

    
        select * from mybatis.blog where 1=1
        
            and title =#{title}
        
        
            and author =#{author}
        
    

MyTest:

import com.kuang.dao.BlogMapper;
import com.kuang.pojo.Blog;
import com.kuang.utils.IDUtils;
import com.kuang.utils.MybaitsUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.Date;
import java.util.HashMap;
import java.util.List;


public class MyTest {
    @Test
    public void addBlogTest(){
        SqlSession sqlSession = MybaitsUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);

        Blog blog = new Blog();
        blog.setId(IDUtils.getId());
        blog.setTitle("Mybatis如此简单");
        blog.setAuthor("狂神说");
        blog.setCreateTime(new Date());
        blog.setViews(9999);

        mapper.addBlog(blog);

        blog.setId(IDUtils.getId());
        blog.setTitle("Java如此简单");
        mapper.addBlog(blog);

        blog.setId(IDUtils.getId());
        blog.setTitle("Spring");
        mapper.addBlog(blog);

        blog.setId(IDUtils.getId());
        blog.setTitle("微服务如此简单");
        mapper.addBlog(blog);

        sqlSession.close();
    }

    @Test
    public void queryBlogIF(){
        SqlSession sqlSession=MybaitsUtils.getSqlSession();
        BlogMapper mapper=sqlSession.getMapper(BlogMapper.class);

        HashMap map=new HashMap();
       // map.put("author","狂神说");
       map.put("title","Java如此简单");
        List blogs = mapper.queryBlogIF(map);
        for (Blog blog : blogs) {
            System.out.println(blog);
        }
        sqlSession.close();
    }
}

运行addTestBlogTest：往表中插入数据

queryBlogIF：

 

切换map注释：

 

 BlogMapper：

package com.kuang.dao;

import com.kuang.pojo.Blog;

import java.util.List;
import java.util.Map;

public interface BlogMapper {
    //插入数据
    int addBlog(Blog blog);

    //查询博客
    List queryBlogIF(Map map);

    //
    List queryBlogChoose(Map map);

    //更新博客
    int UpdateBlog(Map map);

    //查询第1-3号记录的博客
    List queryBlogForeach(Map map);
}

BlogMapper.xml:动态sql常用标签

    

    
        insert into mybatis.blog (id, title, author, create_time, views)
        values (#{id},#{title},#{author},#{createTime},#{views});
    

    

    
        select * from mybatis.blog
        
        
            title =#{title}
        
        
            and author =#{author}
        
        
    


    
        select * from mybatis.blog
        
           
            
                 title =#{title}
            
            
                and author =#{author}
            
            
                and views=#{views}
            
           
        
    

    
        update mybatis.blog
        
            
                title=#{title},
            
            
                author=#{author}
            
        
        where id=#{id}
    

MyTest:

import com.kuang.dao.BlogMapper;
import com.kuang.pojo.Blog;
import com.kuang.utils.IDUtils;
import com.kuang.utils.MybaitsUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;


public class MyTest {
    //插入数据
    @Test
    public void addBlogTest(){
        SqlSession sqlSession = MybaitsUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);

        Blog blog = new Blog();
        blog.setId(IDUtils.getId());
        blog.setTitle("Mybatis如此简单");
        blog.setAuthor("狂神说");
        blog.setCreateTime(new Date());
        blog.setViews(9999);

        mapper.addBlog(blog);

        blog.setId(IDUtils.getId());
        blog.setTitle("Java如此简单");
        mapper.addBlog(blog);

        blog.setId(IDUtils.getId());
        blog.setTitle("Spring");
        mapper.addBlog(blog);

        blog.setId(IDUtils.getId());
        blog.setTitle("微服务如此简单");
        mapper.addBlog(blog);

        sqlSession.close();
    }

    //where标签查询
    @Test
    public void queryBlogIF(){
        SqlSession sqlSession=MybaitsUtils.getSqlSession();
        BlogMapper mapper=sqlSession.getMapper(BlogMapper.class);

        HashMap map=new HashMap();
        map.put("author","狂神说");
        //map.put("title","Java如此简单");
        List blogs = mapper.queryBlogIF(map);
        for (Blog blog : blogs) {
            System.out.println(blog);
        }
        sqlSession.close();
    }
    //Choose查询，相当于switch它会找满足条件的一个
    @Test
    public void queryBlogChoose(){
        SqlSession sqlSession=MybaitsUtils.getSqlSession();
        BlogMapper mapper=sqlSession.getMapper(BlogMapper.class);

        HashMap map=new HashMap();
        map.put("title","Java如此简单");
        map.put("author","狂神说");
        map.put("views",9999);

        List blogs = mapper.queryBlogChoose(map);
        for (Blog blog : blogs) {
            System.out.println(blog);
        }
        sqlSession.close();
    }

    //Set更新
    @Test
    public void UpdateBlog(){
        SqlSession sqlSession=MybaitsUtils.getSqlSession();
        BlogMapper mapper=sqlSession.getMapper(BlogMapper.class);

        HashMap map=new HashMap();
        map.put("author","狂神说1");
        map.put("title","Java如此简单");
        map.put("id","311ace05e43747b49db2cc2ff61b687e");

        int i = mapper.UpdateBlog(map);
        if (i>0){
            System.out.println("更新成功");
        }

        sqlSession.close();
    }
    //查询第1-3号记录的博客
    @Test
    public void queryBlogForeach(){
        SqlSession sqlSession=MybaitsUtils.getSqlSession();
        BlogMapper mapper=sqlSession.getMapper(BlogMapper.class);

        HashMap map=new HashMap();

        ArrayList ids=new ArrayList();
        ids.add(1);
        ids.add(2);
        ids.add(3);

        map.put("ids",ids);
        List blogs = mapper.queryBlogForeach(map);
        for (Blog blog : blogs) {
            System.out.println(blog);
        }

        sqlSession.close();
    }
}

queryBlogIF 

 queryBlogChoose:

choose相当于switch只会在查找满足条件的一个，如果把注释的内容打开，只会第一个条件生效  

 

UpdateBlog：

 

 

 

 

 

 

 

 BlogMapper.xml:

    

    
        insert into mybatis.blog (id, title, author, create_time, views)
        values (#{id},#{title},#{author},#{createTime},#{views});
    

    


    
        
            title =#{title}
        
        
            and author =#{author}
        
    


    
        select * from mybatis.blog
        
          
        
    


    
        select * from mybatis.blog
        
           
            
                 title =#{title}
            
            
                and author =#{author}
            
            
                and views=#{views}
            
           
        
    

    
        update mybatis.blog
        
            
                title=#{title},
            
            
                author=#{author}
            
        
        where id=#{id}
    



    
        select * from mybatis.blog
        
            
                id=#{id}
            
        
    

queryBlogForeach：

当不忘List集合中添加id

/*ids.add(1);
ids.add(2);
ids.add(3);*/

 去掉注释：