SpringBoot整合Mybatis注解版

javax.persistence jar的作用 实体类采用注解版

    javax.persistence
    persistence-api
    1.0

1 简约版：

项目结构：

实体类：Employee

public class Employee {

      private Integer id;
      private String name;
      private Double salary;
      private Integer age;

    public Employee(Integer id, String name, Double salary, Integer age) {
        this.id = id;
        this.name = name;
        this.salary = salary;
        this.age = age;
    }

    public Employee() {
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }


    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }


    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }


    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", salary=" + salary +
                ", age=" + age +
                '}';
    }

    public Employee(String name, Double salary, Integer age) {
        this.name = name;
        this.salary = salary;
        this.age = age;
    }
}

mapper接口：

/*mapper接口*/

//1 @Mapper将UserDao声明为一个Mapper接口
//2 @Results是结果映射列表，@Result中property是User类的属性名，colomn是数据库表的字段名
//3 @Select, @Insert 分别代表了执行的真实SQL

@Component
@Mapper
public interface EmployeeMapper {
       @Select("select * from employee where age=#{age}")
       List get(int age);
       @Insert("insert into employee(name,salary,age) value(#{name},#{salary},#{age})")
       void insert(Employee employee);


}

/*mapper接口*/

//1 @Mapper将UserDao声明为一个Mapper接口
//2 @Results是结果映射列表，@Result中property是User类的属性名，colomn是数据库表的字段名
//3 @Select, @Insert 分别代表了执行的真实SQL

@Component
@Mapper
public interface EmployeeMapper {
       @Select("select * from employee where age=#{age}")
       List get(int age);
       @Insert("insert into employee(name,salary,age) value(#{name},#{salary},#{age})")
       void insert(Employee employee);


}

EmployeeController:

@Controller
public class EmployeeController {

    @Autowired //自动连接到UserService Bean
    private EmployeeMapper employeeMapper;

    @RequestMapping(value = "/show")
    @ResponseBody
    public String show() {
        return "ok";
    }

    @RequestMapping(value = "/get")
    @ResponseBody
        public Object get(int age) {

        return employeeMapper.get(age);
    }

    @RequestMapping(value=/insert")
    public String insert() {
        Employee employee=new Employee("tom",12000.0,25);
         employeeMapper.insert(employee);
        return "ok";
    }
}

SpringBoot启动类：注意这里要扫描mapper接口的所在包

@SpringBootApplication
@MapperScan(basePackages = "yiche.com.mapper")
public class MyApplication {
    public static void main(String[] args){
        SpringApplication.run(MyApplication.class,args);
    }
}

application.properties

pom 文件：

  org.springframework.boot
  spring-boot-starter-web



  org.mybatis.spring.boot
  mybatis-spring-boot-starter
  1.1.1



  mysql
  mysql-connector-java
  5.1.21




  javax.persistence
  persistence-api
  1.0

下面SpringBoot整合Mybatis注解升级版：

  三张表之间的关联查询     user  -->多个orders    

                                         order --> 多个orderItem

  建表sql如下

CREATE TABLE USER(
  uid INT NOT NULL AUTO_INCREMENT,
  NAME VARCHAR(50),
  PRIMARY KEY(uid)
);




CREATE TABLE orders(
  oid INT NOT NULL AUTO_INCREMENT,
  NAME VARCHAR(50),
  uid INT,
  PRIMARY KEY(oid),
  FOREIGN KEY(uid) REFERENCES USER(uid)
);


CREATE TABLE orderItem(
  id INT NOT NULL AUTO_INCREMENT,
  NAME VARCHAR(50),
  oid INT,
  PRIMARY KEY(id),
  FOREIGN KEY(oid) REFERENCES orders(oid)
)

实体类：

public class User {
     private Integer uid;
     private String name;
     private List orders;

}

public class Orders {
     private  Integer oid ;
     private  String name;
     private  User user;
     private  List orderItems;

}

public class OrderItem {
     private Integer id;
     private String  name;
     private Orders orders;

}

userMapper中的接口重新定义方法

  

@Select("select * from user where uid=#{id}")
User getUserById(int id);

和如下的这种写法一致

@Select("select * from user where uid=#{id}")
       @Results({
               @Result(property = "uid", column = "uid"),
               @Result(property = "name", column = "name")
       })

       User getUserById(int id);

Controller：

@RequestMapping(value="/getUser")
@ResponseBody
public User getUser() {
    int id=1;
    User user= employeeMapper.getUserById(id);
    return user;
}

结果： 查到的orders属性为为null  因为还没和ordes属性建立关联

下面建立联系

 上面得到uid  还需要在order中写方法 根据外键uid得到orders的方法 

在OrderMapper中定义方法

public interface OrderMapper {

        //根据外键获得orders的方法
        @Select("select * from orders where uid=#{uid}")
        List getOrdersByUid(int uid);
}

然后修改原来userMapper接口中的方法因为要填充属性原来的方法sql不满足条件

注意：properties=“orders”是 User实体类中的属性 

       column="uid" 是orders表中的外键

@Select("select * from user where uid=#{id}")
@Results({
        @Result(property = "uid", column = "uid"),
        @Result(property = "name", column = "name"),
        @Result(
                property = "orders",
                column = "uid",
                many = @Many(select="yiche.com.mapper.OrderMapper.getOrdersByUid")
        )
})
User getUserById(int id);

结果：  此时orders已经有值  但是orders中的属性 orderItems还没有值  user也没有值  用同理的方法可以实现值  

现在把orderItem完善值 ：

 在OrderItemMapper添加工具外键获取OrderItem的方法

public interface OrderItemMapper {

       @Select("select * from orderitem where oid=#{oid}")
       List getOrderItemByOid();

}

在修改OrderMapper接口原来的方法 让order的属性和orderItem建立联系

public interface OrderMapper {

        //根据外键获得orders的方法
        @Select("select * from orders where uid=#{uid}")
        @Results(
                {
                        @Result(property = "oid", column = "oid"),
                        @Result(property = "name", column = "name"),
                        @Result(
                                property = "orderItems",
                                column = "oid",
                                many = @Many(select = "yiche.com.mapper.OrderItemMapper.getOrderItemByOid")
                        )
                }
        )
        List getOrdersByUid(int uid);
}

访问：controller        getUser方法

结果：打印 orderitem已经有值

{"uid":1,"name":"tom","orders":[{"oid":1,"name":"a-order","user":null,"orderItems":[{"id":1,"name":"apple","orders":null},{"id":2,"name":"paper","orders":null}]},{"oid":2,"name":"b-order","user":null,"orderItems":[{"id":3,"name":"dirnk","orders":null},{"id":4,"name":"pel","orders":null}]}]}

同理：@用@one的方法同样可以把orders里面的user   orderItem里面的order完善值

@One @Many的总结

注意

同点：
- 无论是一对一还是一对多，都是通过附属查询来实现的，我们需要定义这个附属查询方法。
- 在主查询方法中通过@One、@Many指定附属查询方法的全路径。
- 都通过column来传递参数给附属方法。

不同点：
- 一对一，那么附属方法返回的是一个单独的对象

- 一对多，那么附属方法返回的是一个对象集合

接下来看的内容：动态语言注解：

（1）动态语言注解
（2）@Provider使用思路
（3）@SelectProvider小试牛刀
（4）@SelectProvider初露锋芒
（5）@SelectProvider过关斩将
（6）@InsertProvider小弟不敢当
（7）@UpdateProvider你加我来改

（8）@DeleteProvider不高兴就删

使用的方式就是编写一个类 SqlProvide 提供sql语句  而mapper接口使用对应的注解

public class SqlProvide {


         public String select1(Employee employee){


               StringBuilder sql=new StringBuilder();
               sql.append("select * from employee where 1=1");
               if (employee.getName() != null){
                   sql.append(" and name=#{name}");
               }


               if (employee.getAge() != null){
                   sql.append(" and age=#{age}");
               }




               return  sql.toString();
         }

}

EmployeeMapper使用对应的注解：

 @SelectProvider(type = SqlProvide.class,method = "select1")

       Employee  getEmployeeBy(Employee employee);

Controller方法：

   
    @RequestMapping(value="/testsql")
    @ResponseBody
    public Employee testSql() {


        Employee employee=new Employee();
        employee.setName("jack");
        employee.setAge(22);


        employee=employeeMapper.getEmployeeBy(employee);
        return employee;

    }

结果：

{"id":2,"name":"jack","salary":11000.0,"age":22}

上面的代码直接纯SQL编写了，可读性还是相对差了点，MyBatis提供了SQL类（org.apache.ibatis.jdbc.SQL），可以让代码看起来更有意义。

 修改SqlProvide方法

   public String select1(Employee employee){
             return new SQL(){{
                 SELECT("*");
                 FROM("employee");
                 if (employee.getName() != null){


                     WHERE("name=#{name}");


                    }


                 if (employee.getAge() != null){
                     WHERE("age=#{age}");


                    }
               }}.toString();

         }

结果一样

{"id":2,"name":"jack","salary":11000.0,"age":22}

其余的参考：

http://412887952-qq-com.iteye.com/blog/2391924