springboot 和 mybatis整合:参数查询和动态sql

springboot 和 mybatis整合：

mapper定义的是数据库的操作方法:

@Mapper
public interface UserMapper {
     }

单参数的处理：

    @Select("select * from t_user")
    @Results({
     
            @Result(property = "userId", column = "USER_ID"),
            @Result(property = "username", column = "USERNAME"),
            @Result(property = "password", column = "PASSWORD"),
            @Result(property = "mobileNum", column = "PHONE_NUM")
    })
    List<User> list();

多参数的处理：

    /**
     * 延伸：无论什么方式,如果涉及多个参数,则必须加上@Param注解,否则无法使用EL表达式获取参数。
     */
    @Select("select * from t_user where username like #{username} and password like #{password}")
    @Results({
     
            @Result(property = "userId", column = "USER_ID"),
            @Result(property = "username", column = "USERNAME"),
            @Result(property = "password", column = "PASSWORD"),
            @Result(property = "mobileNum", column = "PHONE_NUM")
    })
    User get(@Param("username") String username, @Param("password") String password);

CRUD的高级注解：

@SelectProvider
@InsertProvider
@UpdateProvider
@DeleteProvider

先在mapper下定义Provider，所谓的Provider就是自定义的sql语句，规则可以自定义

public class UserSqlProvider {
     
    /**
     * 方式1：在工具类的方法里,可以自己手工编写SQL。
     */
    public String listByUsername(String username) {
     
        return "select * from t_user where username =#{username}";
    }
}

然后定义使用这个sql语句的方法，就在对应的mapper里面操作：

    /**
     * 方式2：使用注解指定某个工具类的方法来动态编写SQL.
     */
    @SelectProvider(type = UserSqlProvider.class, method = "listByUsername")
    @Results({
     
            @Result(property = "userId", column = "USER_ID"),
            @Result(property = "username", column = "USERNAME"),
            @Result(property = "password", column = "PASSWORD"),
            @Result(property = "mobileNum", column = "PHONE_NUM")
    })
    List<User> listByUsername(String username);

controller里面使用：

    @GetMapping("list/{username}")
    public List<User> listByUsername(@PathVariable("username") String username) {
     
        return userMapper.listByUsername(username);
    }

another samples:

UserSqlProvider.java   

/**
     * 方式2：也可以根据官方提供的API来编写动态SQL。
     */
    public String getBadUser(@Param("username") String username, @Param("password") String password) {
     
        return new SQL() {
     {
     
            SELECT("*");
            FROM("t_user");
            if (username != null && password != null) {
     
                WHERE("username like #{username} and password like #{password}");
            } else {
     
                WHERE("1=2");
            }
        }}.toString();
    }

UserMapper.java

    @SelectProvider(type = UserSqlProvider.class, method = "getBadUser")
    @Results({
     
            @Result(property = "userId", column = "USER_ID"),
            @Result(property = "username", column = "USERNAME"),
            @Result(property = "password", column = "PASSWORD"),
            @Result(property = "mobileNum", column = "PHONE_NUM")
    })
    User getBadUser(@Param("username") String username, @Param("password") String password);

UserController.java
    @GetMapping("get/bad/{username}/{password}")
    public User getBadUser(@PathVariable("username") String username, @PathVariable("password") String password) {
     
        return userMapper.getBadUser(username, password);
    }