376 lines
11 KiB
Markdown
376 lines
11 KiB
Markdown
# 精尽 MyBatis 源码分析 —— 调试环境搭建
|
||
|
||
# 1. 依赖工具
|
||
|
||
- Maven
|
||
- Git
|
||
- JDK
|
||
- IntelliJ IDEA
|
||
|
||
# 2. 源码拉取
|
||
|
||
从官方仓库 https://github.com/mybatis/mybatis-3 `Fork` 出属于自己的仓库。为什么要 `Fork` ？既然开始阅读、调试源码，我们可能会写一些注释，有了自己的仓库，可以进行自由的提交。😈
|
||
|
||
使用 `IntelliJ IDEA` 从 `Fork` 出来的仓库拉取代码。
|
||
|
||
本文使用的 MyBatis 版本为 `3.5.0-SNAPSHOT` 。
|
||
|
||
因为 MyBatis 是有些年份的框架，所以克隆的过程可能比较慢，耐心等待。
|
||
|
||
# 3. 调试
|
||
|
||
MyBatis 想要调试，非常方便，只需要打开 `org.apache.ibatis.autoconstructor.AutoConstructorTest` 单元测试类，任意一个单元测试方法，右键，开始调试即可。
|
||
|
||
当然，考虑到让大家更好的理解 AutoConstructorTest 这个类，下面，我们还是详细解析下。AutoConstructorTest 所在在 `autoconstructor` 包下，整体结构如下：
|
||
|
||
[](http://static.iocoder.cn/images/MyBatis/2020_01_01/01.jpg)包结构图
|
||
|
||
# 4. mybatis-config.xml
|
||
|
||
`mybatis-config.xml` ，MyBatis 配置文件。XML 如下：
|
||
|
||
```
|
||
<!DOCTYPE configuration
|
||
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
|
||
"http://mybatis.org/dtd/mybatis-3-config.dtd">
|
||
|
||
<configuration>
|
||
|
||
<!-- autoMappingBehavior should be set in each test case -->
|
||
|
||
<environments default="development">
|
||
<environment id="development">
|
||
<!-- 配置事务管理 -->
|
||
<transactionManager type="JDBC">
|
||
<property name="" value=""/>
|
||
</transactionManager>
|
||
<!-- 配置数据源 -->
|
||
<dataSource type="UNPOOLED">
|
||
<property name="driver" value="org.hsqldb.jdbcDriver"/>
|
||
<property name="url" value="jdbc:hsqldb:mem:automapping"/>
|
||
<property name="username" value="sa"/>
|
||
</dataSource>
|
||
</environment>
|
||
</environments>
|
||
|
||
<!-- 扫描 Mapper 文件 -->
|
||
<mappers>
|
||
<mapper resource="org/apache/ibatis/autoconstructor/AutoConstructorMapper.xml"/>
|
||
</mappers>
|
||
|
||
</configuration>
|
||
```
|
||
|
||
- 在 `<environments />` 标签中，配置了事务管理和数据源。考虑到减少外部依赖，所以使用了 [HSQLDB](https://zh.wikipedia.org/wiki/HSQLDB) 。
|
||
- 在 `<mappers />` 标签中，配置了需要扫描的 Mapper 文件。目前，仅仅扫描 `AutoConstructorMapper.xml` 文件。
|
||
|
||
# 5. AutoConstructorMapper.xml
|
||
|
||
`AutoConstructorMapper.xml` ，Mapper 文件。代码如下：
|
||
|
||
```
|
||
<!DOCTYPE mapper
|
||
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
|
||
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
|
||
|
||
<mapper namespace="org.apache.ibatis.autoconstructor.AutoConstructorMapper">
|
||
</mapper>
|
||
```
|
||
|
||
- 对应的接口为 `org.apache.ibatis.autoconstructor.AutoConstructorMapper` 。
|
||
|
||
## 5.1 AutoConstructorMapper
|
||
|
||
```
|
||
public interface AutoConstructorMapper {
|
||
|
||
// ========== PrimitiveSubject ==========
|
||
|
||
@Select("SELECT * FROM subject WHERE id = #{id}")
|
||
PrimitiveSubject getSubject(final int id);
|
||
@Select("SELECT * FROM subject")
|
||
List<PrimitiveSubject> getSubjects();
|
||
|
||
// ========== AnnotatedSubject ==========
|
||
|
||
@Select("SELECT * FROM subject")
|
||
List<AnnotatedSubject> getAnnotatedSubjects();
|
||
|
||
// ========== BadSubject ==========
|
||
|
||
@Select("SELECT * FROM subject")
|
||
List<BadSubject> getBadSubjects();
|
||
|
||
// ========== ExtensiveSubject ==========
|
||
|
||
@Select("SELECT * FROM extensive_subject")
|
||
List<ExtensiveSubject> getExtensiveSubject();
|
||
|
||
}
|
||
```
|
||
|
||
- 使用注解的方法，编写 SQL 。
|
||
|
||
# 6. CreateDB.sql
|
||
|
||
`CreateDB.sql` 文件，用于单元测试里，初始化数据库的数据。如下：
|
||
|
||
```
|
||
DROP TABLE subject
|
||
IF EXISTS;
|
||
|
||
DROP TABLE extensive_subject
|
||
IF EXISTS;
|
||
|
||
CREATE TABLE subject (
|
||
id INT NOT NULL,
|
||
name VARCHAR(20),
|
||
age INT NOT NULL,
|
||
height INT,
|
||
weight INT,
|
||
active BIT,
|
||
dt TIMESTAMP
|
||
);
|
||
|
||
CREATE TABLE extensive_subject (
|
||
aByte TINYINT,
|
||
aShort SMALLINT,
|
||
aChar CHAR,
|
||
anInt INT,
|
||
aLong BIGINT,
|
||
aFloat FLOAT,
|
||
aDouble DOUBLE,
|
||
aBoolean BIT,
|
||
aString VARCHAR(255),
|
||
anEnum VARCHAR(50),
|
||
aClob LONGVARCHAR,
|
||
aBlob LONGVARBINARY,
|
||
aTimestamp TIMESTAMP
|
||
);
|
||
|
||
INSERT INTO subject VALUES
|
||
(1, 'a', 10, 100, 45, 1, CURRENT_TIMESTAMP),
|
||
(2, 'b', 10, NULL, 45, 1, CURRENT_TIMESTAMP),
|
||
(2, 'c', 10, NULL, NULL, 0, CURRENT_TIMESTAMP);
|
||
|
||
INSERT INTO extensive_subject
|
||
VALUES
|
||
(1, 1, 'a', 1, 1, 1, 1.0, 1, 'a', 'AVALUE', 'ACLOB', 'aaaaaabbbbbb', CURRENT_TIMESTAMP),
|
||
(2, 2, 'b', 2, 2, 2, 2.0, 2, 'b', 'BVALUE', 'BCLOB', '010101010101', CURRENT_TIMESTAMP),
|
||
(3, 3, 'c', 3, 3, 3, 3.0, 3, 'c', 'CVALUE', 'CCLOB', '777d010078da', CURRENT_TIMESTAMP);
|
||
```
|
||
|
||
- 创建了 `subject` 表，并初始化三条数据。
|
||
- 创建了 `extensive_subject` 表，并初始化三条数据。
|
||
|
||
# 7. POJO
|
||
|
||
在 AutoConstructorMapper 中，我们可以看到有四个 POJO 类。但是，从 `CreateDB.sql` 中，实际只有两个表。这个是为什么呢？继续往下看噢。
|
||
|
||
## 7.1 AnnotatedSubject
|
||
|
||
```
|
||
package org.apache.ibatis.autoconstructor;
|
||
|
||
import org.apache.ibatis.annotations.AutomapConstructor;
|
||
|
||
public class AnnotatedSubject {
|
||
|
||
private final int id;
|
||
private final String name;
|
||
private final int age;
|
||
private final int height;
|
||
private final int weight;
|
||
|
||
public AnnotatedSubject(final int id, final String name, final int age, final int height, final int weight) {
|
||
this.id = id;
|
||
this.name = name;
|
||
this.age = age;
|
||
this.height = height;
|
||
this.weight = weight;
|
||
}
|
||
|
||
@AutomapConstructor
|
||
public AnnotatedSubject(final int id, final String name, final int age, final Integer height, final Integer weight) {
|
||
this.id = id;
|
||
this.name = name;
|
||
this.age = age;
|
||
this.height = height == null ? 0 : height;
|
||
this.weight = weight == null ? 0 : weight;
|
||
}
|
||
|
||
}
|
||
```
|
||
|
||
- 对应 `subject` 表。
|
||
|
||
- ```
|
||
@AutomapConstructor
|
||
```
|
||
|
||
|
||
|
||
注解，表示 MyBatis 查询后，在创建 AnnotatedSubject 对象，使用该构造方法。
|
||
|
||
- 😈 实际场景下，非常少使用这个注解，甚至 Google 上资料也不多。
|
||
|
||
### 7.1.1 PrimitiveSubject
|
||
|
||
```
|
||
package org.apache.ibatis.autoconstructor;
|
||
|
||
import java.util.Date;
|
||
|
||
public class PrimitiveSubject {
|
||
|
||
private final int id;
|
||
private final String name;
|
||
private final int age;
|
||
private final int height;
|
||
private final int weight;
|
||
private final boolean active;
|
||
private final Date dt;
|
||
|
||
public PrimitiveSubject(final int id, final String name, final int age, final int height, final int weight, final boolean active, final Date dt) {
|
||
this.id = id;
|
||
this.name = name;
|
||
this.age = age;
|
||
this.height = height;
|
||
this.weight = weight;
|
||
this.active = active;
|
||
this.dt = dt;
|
||
}
|
||
|
||
}
|
||
```
|
||
|
||
- 对应的也是 `subject` 表。
|
||
|
||
- 和 AnnotatedSubject 不同，在其构造方法上，`weight` 和 `height` 方法参数的类型是 `int` ，而不是 Integer
|
||
|
||
。那么，如果 `subject` 表中的记录，这两个字段为 `NULL` 时，会创建 PrimitiveSubject 对象报错。
|
||
|
||
### 7.1.2 BadSubject
|
||
|
||
```
|
||
package org.apache.ibatis.autoconstructor;
|
||
|
||
public class BadSubject {
|
||
|
||
private final int id;
|
||
private final String name;
|
||
private final int age;
|
||
private final Height height;
|
||
private final Double weight;
|
||
|
||
public BadSubject(final int id, final String name, final int age, final Height height, final Double weight) {
|
||
this.id = id;
|
||
this.name = name;
|
||
this.age = age;
|
||
this.height = height;
|
||
this.weight = weight == null ? 0 : weight;
|
||
}
|
||
|
||
private class Height {
|
||
|
||
}
|
||
|
||
}
|
||
```
|
||
|
||
- 对应的也是 `subject` 表。
|
||
- 和 AnnotatedSubject 不同，在其构造方法上，`height` 方法参数的类型是 Height ，而不是 Integer 。因为 MyBatis 无法识别 Height 类，所以会创建 BadSubject 对象报错。
|
||
|
||
> 老艿艿：一般情况下，POJO 对象里，不使用基本类型。
|
||
|
||
## 7.2 ExtensiveSubject
|
||
|
||
```
|
||
package org.apache.ibatis.autoconstructor;
|
||
|
||
public class ExtensiveSubject {
|
||
private final byte aByte;
|
||
private final short aShort;
|
||
private final char aChar;
|
||
private final int anInt;
|
||
private final long aLong;
|
||
private final float aFloat;
|
||
private final double aDouble;
|
||
private final boolean aBoolean;
|
||
private final String aString;
|
||
|
||
// enum types
|
||
private final TestEnum anEnum;
|
||
|
||
// array types
|
||
|
||
// string to lob types:
|
||
private final String aClob;
|
||
private final String aBlob;
|
||
|
||
public ExtensiveSubject(final byte aByte,
|
||
final short aShort,
|
||
final char aChar,
|
||
final int anInt,
|
||
final long aLong,
|
||
final float aFloat,
|
||
final double aDouble,
|
||
final boolean aBoolean,
|
||
final String aString,
|
||
final TestEnum anEnum,
|
||
final String aClob,
|
||
final String aBlob) {
|
||
this.aByte = aByte;
|
||
this.aShort = aShort;
|
||
this.aChar = aChar;
|
||
this.anInt = anInt;
|
||
this.aLong = aLong;
|
||
this.aFloat = aFloat;
|
||
this.aDouble = aDouble;
|
||
this.aBoolean = aBoolean;
|
||
this.aString = aString;
|
||
this.anEnum = anEnum;
|
||
this.aClob = aClob;
|
||
this.aBlob = aBlob;
|
||
}
|
||
|
||
public enum TestEnum {
|
||
AVALUE, BVALUE, CVALUE;
|
||
}
|
||
|
||
}
|
||
```
|
||
|
||
- 对应的也是 `extensive_subject` 表。
|
||
- 这是个复杂对象，基本涵盖了各种类型的数据。
|
||
|
||
# 8. AutoConstructorTest
|
||
|
||
`org.apache.ibatis.autoconstructor.AutoConstructorTest` ，单元测试类。
|
||
|
||
## 8.1 setUp
|
||
|
||
```
|
||
private static SqlSessionFactory sqlSessionFactory;
|
||
|
||
@BeforeClass
|
||
public static void setUp() throws Exception {
|
||
// create a SqlSessionFactory
|
||
// 创建 SqlSessionFactory 对象，基于 mybatis-config.xml 配置文件。
|
||
try (Reader reader = Resources.getResourceAsReader("org/apache/ibatis/autoconstructor/mybatis-config.xml")) {
|
||
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
|
||
}
|
||
|
||
// populate in-memory database
|
||
// 初始化数据到内存数据库，基于 CreateDB.sql SQL 文件。
|
||
BaseDataTest.runScript(sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(),
|
||
"org/apache/ibatis/autoconstructor/CreateDB.sql");
|
||
}
|
||
```
|
||
|
||
- 创建 SqlSessionFactory 对象，基于 `mybatis-config.xml` 配置文件。
|
||
- 初始化数据到内存数据库，基于 `CreateDB.sql` SQL 文件。
|
||
|
||
## 8.2 测试方法
|
||
|
||
右键任一单元测试方法，愉快的调试起来把。 |