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/' target='_blank'>mysql"/>    <property name="offsetAsPageNum" value="true"/>    <property name="rowBoundsWithCount" value="true"/>    <property name="pageSizeZero" value="true"/>  </plugin></plugins>

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