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 + "\t对应的分类是：\t" + 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("\t%s\t%f\t%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());
}
}
}
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