mybatis-user-guide

date: 2016-01-06 20:28:17

  1. java注解
  2. settings 参数配置
  3. 自定义类处理器
  4. plugins 拦截
  5. environments 可以配置多种环境，将sql映射应用于多种数据库之中。
  6. transactioinManager 事务管理 创建事务接口的实现，自定义事务管理
  7. assocation 关联查询 复杂对象映射
  8. discriminator 鉴别器
  9. cache 自定义缓存
  10. 动态sql

源码阅读心得：

  1. SqlSessionFactoryBuilder， SqlSessionFactory， SqlSession
  1. 构建SqlSessionFactory
    a. 从xml构建
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    <?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
    <environments default="development">
    <environment id="development">
    <transactionManager type="JDBC"/>
    <dataSource type="POOLED">
    <property name="driver" value="${driver}"/>
    <property name="url" value="${url}"/>
    <property name="username" value="${username}"/>
    <property name="password" value="${password}"/>
    </dataSource>
    </environment>
    </environments>
    <mappers>
    <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    </mappers>
    </configuration>

b.通过java程序构建

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DataSource dataSource = BlogDataSourceFactory.getBlogDataSource();
TransactionFactory transactionFactory = new
JdbcTransactionFactory();
Environment environment = new Environment("development", transactionFactory, dataSource);
Configuration configuration = new Configuration(environment);
configuration.addMapper(BlogMapper.class);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(configuration);

  1. 简单的sql语句可以用java注解完成

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    package org.mybatis.example;
    public interface BlogMapper {
    @Select("SELECT * FROM blog WHERE id = #{id}")
    Blog selectBlog(int id);
    }

  2. xml映射配置文件
    a.properties属性

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    <dataSource type="POOLED">
    <property name="driver" value="${driver}"/>
    <property name="url" value="${url}"/>
    <property name="username" value="${username}"/>
    <property name="password" value="${password}"/>
    </dataSource>

b.settings设置
这个属性极其重要，他会改变mybatis运行时的方式，配置如下：

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<settings>
<setting name="cacheEnabled" value="true"/>
<setting name="lazyLoadingEnabled" value="true"/>
<setting name="multipleResultSetsEnabled" value="true"/>
<setting name="useColumnLabel" value="true"/>
<setting name="useGeneratedKeys" value="false"/>
<setting name="enhancementEnabled" value="false"/>
<setting name="defaultExecutorType" value="SIMPLE"/>
<setting name="defaultStatementTimeout" value="25000"/>
</settings>

c.typeAliases类型别名

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<typeAliases>
<typeAlias alias="Author" type="domain.blog.Author"/>
<typeAlias alias="Blog" type="domain.blog.Blog"/>
<typeAlias alias="Comment" type="domain.blog.Comment"/>
<typeAlias alias="Post" type="domain.blog.Post"/>
<typeAlias alias="Section" type="domain.blog.Section"/>
<typeAlias alias="Tag" type="domain.blog.Tag"/>
</typeAliases>

d.typeHandlers类型处理器
默认的如：

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类型处理器            Java 类型         JDBC 类型
BooleanTypeHandler  Boolean,boolean  任何兼容的布尔值
ByteTypeHandler 	Byte,byte        任何兼容的数字或字节类型

也可以自定义：

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// ExampleTypeHandler.java
public class ExampleTypeHandler implements TypeHandler {
public void setParameter(PreparedStatement ps, int i, Object
parameter,JdbcType jdbcType) throws SQLException {
ps.setString(i, (String) parameter);
}
public Object getResult(ResultSet rs, String columnName)
throws SQLException {
return rs.getString(columnName);
}
public Object getResult(CallableStatement cs, int columnIndex)
throws SQLException {
return cs.getString(columnIndex);
}
}
// MapperConfig.xml
<typeHandlers>
<typeHandler javaType="String" jdbcType="VARCHAR"
handler="org.mybatis.example.ExampleTypeHandler"/>
</typeHandlers>

e.
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