mybatis 项目配置文件实例详解

mybatis项目配置

首先这事一个简单的mybatis项目配置文件：

<?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>

environment

mybatis支持多个环境，可以任意配置

比如：

 <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>

  <environment id="test">
   <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>

就会有两个环境，environments中的defalut标签选择哪一个，默认就是哪一个

transactionManager

mybatis支持两种类型的事务管理器，jdbc和managed（托管）

jdbc：应用程序管理数据库连接的生命周期

managed：由应用服务器负责管理数据库连接的生命周期（一般商业服务器才有此功能，如JBOSS WebLogic）

dataSource

type：用来配置数据源，类型有：UNPOOLED、POOLED、JNDI

UNPOOLED：没有连接池，每次数据库操作，mybatis都会创建一个新的连接，用完后，关闭：适合小并发项目

POOLED：有连接池

JNDI：使用应用服务器配置JNDI数据源获取数据库连接

properties

配置属性

比如：

<properties resource="org/mybatis/example/config.properties">
 <property name="username" value="dev_user"/>
 <property name="password" value="F2Fa3!33TYyg"/>
</properties>

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

typeAliases

给类的完整限定名取别名，方便使用

比如：

<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>
<!-- 最常用-->
<typeAliases>
 <package name="domain.blog"/>
</typeAliases>

mappers

引入映射文件

<!-- Using classpath relative resources -->
<mappers>
 <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
 <mapper resource="org/mybatis/builder/BlogMapper.xml"/>
 <mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>
<!-- Using url fully qualified paths -->
<mappers>
 <mapper url="file:///var/mappers/AuthorMapper.xml"/>
 <mapper url="file:///var/mappers/BlogMapper.xml"/>
 <mapper url="file:///var/mappers/PostMapper.xml"/>
</mappers>
<!-- Using mapper interface classes -->
<mappers>
 <mapper class="org.mybatis.builder.AuthorMapper"/>
 <mapper class="org.mybatis.builder.BlogMapper"/>
 <mapper class="org.mybatis.builder.PostMapper"/>
</mappers>
<!-- Register all interfaces in a package as mappers -->
<mappers>
 <package name="org.mybatis.builder"/>
</mappers>

settings

An example of the settings element fully configured is as follows:

<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="autoMappingBehavior" value="PARTIAL"/>
 <setting name="autoMappingUnknownColumnBehavior" value="WARNING"/>
 <setting name="defaultExecutorType" value="SIMPLE"/>
 <setting name="defaultStatementTimeout" value="25"/>
 <setting name="defaultFetchSize" value="100"/>
 <setting name="safeRowBoundsEnabled" value="false"/>
 <setting name="mapUnderscoreToCamelCase" value="false"/>
 <setting name="localCacheScope" value="SESSION"/>
 <setting name="jdbcTypeForNull" value="OTHER"/>
 <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString"/>
</settings>

plugins

插件 比如：

分页插件

<plugins>
  <plugin interceptor="com.github.pagehelper.PageHelper">
    <property name="dialect" value="mysql"/>
    <property name="offsetAsPageNum" value="true"/>
    <property name="rowBoundsWithCount" value="true"/>
    <property name="pageSizeZero" value="true"/>
  </plugin>
</plugins>

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