初识 tk.mybatis.mapper 通用mapper

在博客园发表Mybatis Dynamic Query后，一位园友问我知不知道通用mapper，仔细去找了一下，还真的有啊，比较好的就是abel533写的tk.mybatis.mapper。
本次例子地址：https://github.com/wz2cool/tk-mybatis-demo

传统Mybatis用法

Spring boot

引用基本的jar到pom

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.4</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <version>1.5.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <version>1.5.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.0</version>
</dependency>

sql 数据准备

DROP TABLE IF EXISTS category;
CREATE TABLE category (
  category_id   INT PRIMARY KEY,
  category_name VARCHAR (50) NOT NULL,
  description   VARCHAR (100)
);
DROP TABLE IF EXISTS product;
CREATE TABLE product (
  product_id    INT PRIMARY KEY auto_increment,
  category_id   INT NOT NULL,
  product_name  VARCHAR (50) NOT NULL,
  price         DECIMAL
);
DELETE FROM category;
INSERT INTO category (category_id, category_name, description) VALUES
  (1, 'Beverages', 'test'),
  (2, 'Condiments', 'test'),
  (3, 'Oil', 'test');
  DELETE FROM product;
INSERT INTO product (product_id, category_id, product_name, price) VALUES
  (1, 1, 'Northwind Traders Chai', 18.0000),
  (2, 2, 'Northwind Traders Syrup', 7.5000),
  (3, 2, 'Northwind Traders Cajun Seasoning', 16.5000),
  (4, 3, 'Northwind Traders Olive Oil', 16.5000),
  (5, 3, 'Northwind Traders Olive Oil2', 16.5000);

entity

public class Product {
    private Integer productID;
    private String productName;
    private BigDecimal price;
    private Integer categoryID;
    // get/set...
}

@Table(name = "category")
public class Category {
    @Id
    @Column(name = "category_id")
    private Integer categoryID;
    private String categoryName;
    private String description;
    // get /set...
}

Dao

这里的ProductDao 是传统的mybatis的用法。

@Mapper
public interface ProductDao {
    List<Product> getProducts();
}

mapper

传统mybatis 咱们必须有个xml 文件和Dao 对应起来, tk.maybatis.mapper无需此文件。

<mapper namespace="com.github.wz2cool.demo.tk.mybatis.mapper.ProductDao">
    <select id="getProducts" resultType="com.github.wz2cool.demo.tk.mybatis.model.entity.table.Product">
        SELECT * FROM product
    </select>
</mapper>

设置扫描包

@SpringBootApplication
@MapperScan(basePackages = "com.github.wz2cool.demo.tk.mybatis.mapper")
public class TestApplication {
    public static void main(String[] args) {
        SpringApplication.run(TestApplication.class, args);
    }
}

application.properies

注意这里的配置只是针对咱们传统mybatis配置，对于tk.maybatis.mapper能够省略这里的配置。

mybatis.type-aliases-package=com.github.wz2cool.demo.tk.mybatis.mapper
mybatis.mapper-locations=classpath:com.github.wz2cool.demo.tk.mybatis.mapper/*.xml

测试

咱们能够简单调用一下

@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(classes = TestApplication.class)
public class SimpleTest {

    @Autowired
    private ProductDao productDao;

    @Test
    public void testSelect() throws Exception {
        List<Product> productList = productDao.getProducts();
        assertEquals(true, productList.size() > 0);
    }
}

咱们能够看到输出结果，基本上就通了

==>  Preparing: SELECT * FROM product 
==> Parameters: 
<==    Columns: PRODUCT_ID, CATEGORY_ID, PRODUCT_NAME, PRICE
<==        Row: 1, 1, Northwind Traders Chai, 18.0000
<==        Row: 2, 2, Northwind Traders Syrup, 7.5000
<==        Row: 3, 2, Northwind Traders Cajun Seasoning, 16.5000
<==        Row: 4, 3, Northwind Traders Olive Oil, 16.5000
<==        Row: 5, 3, Northwind Traders Olive Oil2, 16.5000
<==      Total: 5

tk.mybatis.mapper 用法

添加引用

须要多添加两个引用 (ps:曾经少了一个mapper-spring-boot-starter,报错死活找不到为何--!!!)

<dependency>
    <groupId>tk.mybatis</groupId>
    <artifactId>mapper</artifactId>
    <version>3.4.2</version>
</dependency>
<!--mapper-->
<dependency>
    <groupId>tk.mybatis</groupId>
    <artifactId>mapper-spring-boot-starter</artifactId>
    <version>1.1.3</version>
</dependency>

继承通用mapper

嗯 是的没有xml 文件。

public interface CategoryDao extends Mapper<Category> {
}

测试调用

dao 里面自带不少方法，好比 selectAll(), insert().

@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(classes = TestApplication.class)
public class SimpleTkMapperTest {

    @Autowired
    private CategoryDao categoryDao;

    @Test
    public void selectAllTest() {
        List<Category> categories = categoryDao.selectAll();
        assertEquals(true, categories.size() > 0);
    }

    @Test
    public void insertTest() {
        Category newCategory = new Category();
        newCategory.setCategoryID(1000);
        newCategory.setCategoryName("test");
        newCategory.setDescription("for test");
        int result = categoryDao.insert(newCategory);
        assertEquals(1, result);
    }
}

输出结果

==>  Preparing: SELECT category_id,category_name,description FROM category 
==> Parameters: 
<==    Columns: CATEGORY_ID, CATEGORY_NAME, DESCRIPTION
<==        Row: 1, Beverages, test
<==        Row: 2, Condiments, test
<==        Row: 3, Oil, test
<==      Total: 3


==>  Preparing: INSERT INTO category ( category_id,category_name,description ) VALUES( ?,?,? ) 
==> Parameters: 1000(Integer), test(String), for test(String)
<==    Updates: 1

tk.mybatis.mapper 初步使用感觉

优点

1. 无需xml文件和Dao 对应。
2. 无需指定xml 文件位置（由于就没有xml文件）。
3. 自带多种经常使用方法。

困惑（仅表明我的观点）

1. 自带的方法多可是有些方法理解很晦涩，好比 deleteByExample(Object var1)，这里给一个object 我都不知道要填什么，是填写主键呢仍是这个实体呢？(后来了解其实example 应该是一个筛选条件)

tk.mybatis.mapper(Criteria) 筛选

在理解Example 之后，就开始了解了 Criteria 筛选，固然Example 仍是能够作排序的。
来看看 tk.mybatis.mapper 筛选是如何作的

@Test
public void selectByExampleTest() {
    Example example = new Example(Category.class);
    Example.Criteria criteria = example.createCriteria();
    criteria.andEqualTo("categoryID", 1);
    criteria.orEqualTo("categoryID", 2);
    categoryDao.selectByExample(example);
}

输出结果

==>  Preparing: SELECT category_id,category_name,description FROM category WHERE ( category_id = ? or category_id = ? ) 
==> Parameters: 1(Integer), 2(Integer)
<==    Columns: CATEGORY_ID, CATEGORY_NAME, DESCRIPTION
<==        Row: 1, Beverages, test
<==        Row: 2, Condiments, test
<==      Total: 2

结束

这个只是我初次使用tk.mybatis.mapper 确实不错，能够减小工做量，好像还有能够生成Dao和mapper 的工具，这个我之后再试试看。

要有本身的Mapper

看了 tk.mybatis.mapper 之后，以为通用mapper 也应该加入到 Mybatis Dynamic Query 中去，固然实现可能有点不同。

关于 tk.mybatis.mapper 问题

这里真的想问问园友了

1. tk.mybatis.mapper 支持多表筛选么（join），我本身好像没有找到。
2. tk.mybatis.mapper 支持组么，就是相似于 (id > 1 and id < 5) and price = 10.

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