笔记54 Mybatis快速入门（五）

Mybatis中注解的使用

1.XML方式的CRUD

新增加接口CategoryMapper ，并在接口中声明的方法上，加上注解对比配置文件Category.xml，其实就是把SQL语句从XML挪到了注解上来。

CategoryMapper.java

package mybatis.mapper;

import java.util.List;

import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import mybatis.pojo.Category;

public interface CategoryMapper {
    @Insert("insert into category (name) values (#{name})")
    public int add(Category category);

    @Delete("delete from category where id= #{id}")
    public void delete(int id);

    @Select("select * from category where id= #{id}")
    public Category get(int id);

    @Update("update category set name=#{name} where id=#{id}")
    public int update(Category category);

    @Select("select * from category")
    public List<Category> list();
}

在mybatis-config.xml中增加映射：

<mapper class="mybatis.mapper.CategoryMapper"/>

测试：

package mybatis.annotation;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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

import mybatis.mapper.CategoryMapper;
import mybatis.pojo.Category;

public class testCRUD {
    public static void main(String[] args) throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = org.apache.ibatis.io.Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        CategoryMapper categoryMapper = session.getMapper(CategoryMapper.class);
        add(categoryMapper);
        // listAll(categoryMapper);
        session.commit();
        session.close();

    }

    private static void update(CategoryMapper mapper) {
        Category category = mapper.get(0);
        category.setName("修改了的Category名称");
        mapper.update(category);
        listAll(mapper);
    }

    private static void delete(CategoryMapper mapper) {
        mapper.delete(2);
        listAll(mapper);
    }

    private static void add(CategoryMapper mapper) {
        Category category = new Category();
        category.setName("新增的Category");
        mapper.add(category);
        listAll(mapper);
    }

    private static void get(CategoryMapper mapper) {
        Category category = mapper.get(1);
        System.out.println(category.getName());
    }

    private static void listAll(CategoryMapper mapper) {
        List<Category> cs = mapper.list();
        for (Category c : cs) {
            System.out.println(c.getName());
        }
    }
}

2.一对多

①查询所有Category,通过@Select注解获取Category类本身。@Results 通过@Result和@Many中调用ProductMapper.listByCategory()方法相结合，来获取一对多关系。

    @Select("select * from category")
    @Results({ @Result(property = "id", column = "id"),
               @Result(property = "products", javaType = List.class, column = "id", many = @Many(select = "mybatis.mapper.ProductMapper.listByCategory")) })
    public List<Category> list2();

②新增接口ProductMapper
注解@Select用于根据分类id获取产品集合
@Select(" select * from product_ where cid = #{cid}")

package mybatis.mapper;

import java.util.List;

import org.apache.ibatis.annotations.Select;

import mybatis.pojo.Product;

public interface ProductMapper {
    @Select("select * from product where cid=#{cid}")
    public List<Product> listByCategory(int cid);
}

③添加ProductMapper和CategoryMapper的映射

<mapper class="mybatis.mapper.CategoryMapper"/>
<mapper class="mybatis.mapper.ProductMapper"/>

④结果：

3.多对一

①在CategoryMapper接口中提供get方法

    @Select("select * from category where id= #{id}")
    public Category get(int id);

②在ProductMapper接口中提供list方法

@Select("select * from product")
    @Results({ @Result(property = "id", column = "id"), @Result(property = "name", column = "name"),
            @Result(property = "price", column = "price"),
            @Result(property = "category", column = "cid", one = @One(select = "mybatis.mapper.CategoryMapper.get")) })
    public List<Product> list();

③测试

package mybatis.annotation;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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

import mybatis.mapper.ProductMapper;
import mybatis.pojo.Product;

public class testManyToOne {

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        String resource = "mybatis-config.xml";
        InputStream inputStream = org.apache.ibatis.io.Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        ProductMapper productMapper = session.getMapper(ProductMapper.class);

        List<Product> products = productMapper.list();
        for (Product product : products) {
            System.out.println(product + "	对应的分类是：	" + product.getCategory().getName());
        }

        session.commit();
        session.close();
    }

}

4.多对多

①ProductMapper接口中，新增get方法。

    @Select("select * from product where id=#{id}")
    public Product get(int id);

②新增OrderItemMapper，提供listByOrder方法。
这里会与Product建立多对一关系，一种商品可以出现在多个订单中。

package mybatis.mapper;

import java.util.List;

import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import mybatis.pojo.OrderItem;

public interface OrderItemMapper {
    @Select("select * from order_item where oid=#{oid}")
    @Results({ @Result(property = "id", column = "id"), @Result(property = "number", column = "number"),
            @Result(property = "product", column = "pid", one = @One(select = "mybatis.mapper.ProductMapper.get")) })
    public List<OrderItem> listByOrder(int oid);
}

③新增OrderMapper，提供list方法，这里会与OrderItem建立一对多关系，一个订单中会有多个商品

package mybatis.mapper;

import java.util.List;

import org.apache.ibatis.annotations.Many;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import mybatis.pojo.Order;

public interface OrderMapper {
    @Select("select * from order_")
    @Results({ @Result(property = "id", column = "id"), @Result(property = "code", column = "code"),
            @Result(property = "orderItems", column = "id", javaType = List.class, many = @Many(select = "mybatis.mapper.OrderItemMapper.listByOrder")) })
    public List<Order> list();
}

④修改mybatis-config.xml，增加新的映射。

<mapper class="mybatis.mapper.OrderMapper"/>
<mapper class="mybatis.mapper.OrderItemMapper"/>

⑤测试

package mybatis.annotation;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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

import mybatis.mapper.OrderMapper;
import mybatis.pojo.Order;
import mybatis.pojo.OrderItem;

public class testManyToMany {

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        String resource = "mybatis-config.xml";
        InputStream inputStream = org.apache.ibatis.io.Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        OrderMapper orderMapper = session.getMapper(OrderMapper.class);
        listOrder(orderMapper);
        session.commit();
        session.close();
    }

    private static void listOrder(OrderMapper orderMapper) {
        List<Order> orders = orderMapper.list();
        for (Order order : orders) {
            System.out.println(order.getCode());
            List<OrderItem> orderItems = order.getOrderItems();
            for (OrderItem orderItem : orderItems) {
                System.out.format("	%s	%f	%d%n", orderItem.getProduct().getName(), orderItem.getProduct().getPrice(),
                        orderItem.getNumber());
            }
        }
    }

}

5.动态SQL语句

把手写SQL语句的注解CRUD（1），修改为动态SQL语句方式。

①新增CategoryDynaSqlProvider，提供CRUD对应的SQL语句。这里的SQL语句使用SQL类的方式构建。

package mybatis.dynasql;

import org.apache.ibatis.jdbc.SQL;

public class CategoryDynaSqlProvider {
    public String list() {
        return new SQL().SELECT("*").FROM("category").toString();
    }

    public String get() {
        return new SQL().SELECT("*").FROM("category").WHERE("id=#{id}").toString();
    }

    public String add() {
        return new SQL().INSERT_INTO("category").VALUES("name", "#{name}").toString();
    }

    public String update() {
        return new SQL().UPDATE("category").SET("name=#{name}").WHERE("id=#{id}").toString();
    }

    public String delete() {
        return new SQL().DELETE_FROM("category").WHERE("id=#{id}").toString();
    }
}

②新增CategoryMapperDynaSQL.java

把本来是手写SQL的CategoryMapper接口，修改为注解引用CategoryDynaSqlProvider类的方式。
例如：增加本来是手写SQL语句的

    @Insert("insert into category (name) values (#{name})")
    public int add(Category category);

修改为了注解@InsertProvider配合CategoryDynaSqlProvider的add方法：

@InsertProvider(type = CategoryMapperDynaSQL.class, method = "add")
public int add(Category category);

package mybatis.mapper;

import java.util.List;

import org.apache.ibatis.annotations.DeleteProvider;
import org.apache.ibatis.annotations.InsertProvider;
import org.apache.ibatis.annotations.SelectProvider;
import org.apache.ibatis.annotations.UpdateProvider;

import mybatis.pojo.Category;

public interface CategoryMapperDynaSQL {
    @InsertProvider(type = CategoryMapperDynaSQL.class, method = "add")
    public int add(Category category);

    @DeleteProvider(type = CategoryMapperDynaSQL.class, method = "delete")
    public void delete(int id);

    @SelectProvider(type = CategoryMapperDynaSQL.class, method = "get")
    public Category get(int id);

    @UpdateProvider(type = CategoryMapperDynaSQL.class, method = "update")
    public int update(Category category);

    @SelectProvider(type = CategoryMapperDynaSQL.class, method = "list")
    public List<Category> list();

}

③测试

 

package mybatis.annotation;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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

import mybatis.mapper.CategoryMapperDynaSQL;
import mybatis.pojo.Category;

public class testCRUDDynaSQL {
    public static void main(String[] args) throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = org.apache.ibatis.io.Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        CategoryMapperDynaSQL categoryMapper = session.getMapper(CategoryMapperDynaSQL.class);
        // add(categoryMapper);
        // get(categoryMapper);
        listAll(categoryMapper);
        session.commit();
        session.close();

    }

    private static void update(CategoryMapperDynaSQL mapper) {
        Category category = mapper.get(0);
        category.setName("修改了的Category名称");
        mapper.update(category);
        listAll(mapper);
    }

    private static void delete(CategoryMapperDynaSQL mapper) {
        mapper.delete(2);
        listAll(mapper);
    }

    private static void add(CategoryMapperDynaSQL mapper) {
        Category category = new Category();
        category.setName("新增的Category");
        mapper.add(category);
        listAll(mapper);
    }

    private static void get(CategoryMapperDynaSQL mapper) {
        Category category = mapper.get(1);
        System.out.println(category.getName());
    }

    private static void listAll(CategoryMapperDynaSQL mapper) {
        List<Category> cs = mapper.list();
        for (Category c : cs) {
            System.out.println(c.getName());
        }
    }
}