springboot 和 mybatis整合:參數查詢和動態sql

springboot 和 mybatis整合：

mapper定義的是數據庫的操作方法:

@Mapper
public interface UserMapper {}

單參數的處理：

    @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();

多參數的處理：

    /**
     * 延伸：無論什麼方式,如果涉及多個參數,則必須加上@Param註解,否則無法使用EL表達式獲取參數。
     */
    @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的高級註解：

@SelectProvider
@InsertProvider
@UpdateProvider
@DeleteProvider

先在mapper下定義Provider，所謂的Provider就是自定義的sql語句，規則可以自定義

public class UserSqlProvider {
    /**
     * 方式1：在工具類的方法裏,可以自己手工編寫SQL。
     */
    public String listByUsername(String username) {
        return "select * from t_user where username =#{username}";
    }
}

然後定義使用這個sql語句的方法，就在對應的mapper裏面操作：

    /**
     * 方式2：使用註解指定某個工具類的方法來動態編寫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裏面使用：

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

another samples:

UserSqlProvider.java   

/**
     * 方式2：也可以根據官方提供的API來編寫動態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);
    }