Ibatis配置文件学习

转载自：http://pf-miles.iteye.com/blog/82020

 

iBatis学习笔记：（versions 2.2.0 and higher）

配置文件SqlMapConfig.xml：

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE sqlMapConfig

PUBLIC "-//ibatis.apache.org//DTD SQL Map Config 2.0//EN"

"http://ibatis.apache.org/dtd/sql-map-config-2.dtd">

<!-- Always ensure to use the correct XML header as above! -->

<sqlMapConfig>

<!-- The properties (name=value) in the file specified here can be used placeholders in this config

file (e.g. “${driver}”. The file is relative to the classpath and is completely optional. -->

<properties resource=" examples/sqlmap/maps/SqlMapConfigExample.properties " />

<!-- These settings control SqlMapClient configuration details, primarily to do with transaction

management. They are all optional (more detail later in this document). -->

<settings

cacheModelsEnabled="true"

enhancementEnabled="true"

lazyLoadingEnabled="true"

maxRequests="128"

maxSessions="10"

maxTransactions="5"

useStatementNamespaces="false"

defaultStatementTimeout="5"

statementCachingEnabled="true"

classInfoCacheEnabled="true"

/>

<!-- This element declares a factory class that iBATIS will use for creating result objects.

This element is optional (more detail later in this document). -->

<resultObjectFactory type="com.mydomain.MyResultObjectFactory" >

<property name="someProperty" value="someValue"/>

</resultObjectFactory>

<!-- Type aliases allow you to use a shorter name for long fully qualified class names. -->

<typeAlias alias="order" type="testdomain.Order"/>

<!-- Configure a datasource to use with this SQL Map using SimpleDataSource.

Notice the use of the properties from the above resource -->

<transactionManager type="JDBC" >

<dataSource type="SIMPLE">

<property name="JDBC.Driver" value="${driver}"/>

<property name="JDBC.ConnectionURL" value="${url}"/>

<property name="JDBC.Username" value="${username}"/>

<property name="JDBC.Password" value="${password}"/>

<property name="JDBC.DefaultAutoCommit" value="true" />

<property name="Pool.MaximumActiveConnections" value="10"/>

<property name="Pool.MaximumIdleConnections" value="5"/>

<property name="Pool.MaximumCheckoutTime" value="120000"/>

<property name="Pool.TimeToWait" value="500"/>

<property name="Pool.PingQuery" value="select 1 from ACCOUNT"/>

<property name="Pool.PingEnabled" value="false"/>

<property name="Pool.PingConnectionsOlderThan" value="1"/>

<property name="Pool.PingConnectionsNotUsedFor" value="1"/>

</dataSource>

</transactionManager>

<!-- Identify all SQL Map XML files to be loaded by this SQL map. Notice the paths

are relative to the classpath. For now, we only have one… -->

<sqlMap resource="examples/sqlmap/maps/Person.xml" />

</sqlMapConfig>

其中：

<properties>元素指定了一个标准java properties文件的位置，用classpath相对位置或URL形式指定，之后整个配置文件以及所有被包含进来的映射文件都可以用${key}形式的占位符来获取properties文件中的value值。

<settings>元素：

设置一些全局属性，如延迟加载、缓存模式等。

所有可设置属性及其说明如下：

maxRequests This is the maximum number of threads that can execute an SQL

statement at a time. Threads beyond the set value will be blocked until

another thread completes execution. Different DBMS have different

limits, but no database is without these limits. This should usually be at

least 10 times maxTransactions (see below) and should always be greater

than both maxSessions and maxTransactions. Often reducing the

maximum number of concurrent requests can increase performance.

Example: maxRequests= ”256”

Default: 512

maxSessions This is the number of sessions (or clients) that can be active at a given

time. A session is either an explicit session, requested

programmatically, or it is automatic whenever a thread makes use of an

SqlMapClient instance (e.g. executes a statement etc.). This should

always be greater than or equal to maxTransactions and less than

maxRequests. Reducing the maximum number of concurrent sessions

can reduce the overall memory footprint.

Example: maxSessions= ”64”

Default: 128

maxTransactions This is the maximum number of threads that can enter

SqlMapClient.startTransaction() at a time. Threads beyond the set value

will be blocked until another thread exits. Different DBMS have

different limits, but no database is without these limits. This value

should always be less than or equal to maxSessions and always much

less than maxRequests. Often reducing the maximum number of

concurrent transactions can increase performance.

Example: maxTransactions= ”16”

Default: 32

cacheModelsEnabled This setting globally enables or disables all cache models for an

SqlMapClient. This can come in handy for debugging.

Example: cacheModelsEnabled= ”true”

Default: true (enabled)

lazyLoadingEnabled This setting globally enables or disables all lazy loading for an

SqlMapClient. This can come in handy for debugging.

Example: lazyLoadingEnabled= ”true”

Default: true (enabled)

enhancementEnabled This setting enables runtime bytecode enhancement to facilitate

optimized JavaBean property access as well as enhanced lazy loading.

Example: enhancementEnabled = ”true”

Default: false (disabled)

useStatementNamespaces With this setting enabled, you must always refer to mapped statements

by their fully qualified name, which is the combination of the sqlMap

name and the statement name. For example:

queryForObject(“sqlMapName.statementName”);

Example: useStatementNamespaces= ”false”

Default: false (disabled)

defaultStatementTimeout (iBATIS versions 2.2.0 and later)

This setting is an integer value that will be applied as the JDBC query

timeout for all statements. This value can be overridden with the

“statement” attribute of any mapped statement. If not specified, no

query timeout will be set unless specified on the “statement” attribute of

a mapped statement. The specified value is the number of seconds the

driver will wait for a statement to finish. Note that not all drivers

support this setting.

classInfoCacheEnabled With this setting enabled, iBATIS will maintain a cache of introspected

classes. This will lead to a significant reduction in startup time if many

classes are reused.

Example: classInfoCacheEnabled= “true”

Default: true (enabled)

statementCachingEnabled (iBATIS versions 2.3.0 and later)

With this setting enabled, iBATIS will maintain a local cache of

prepared statements. This can lead to significant performance

improvements.

Example: statementCachingEnabled= “true”

Default: true (enabled)

<resultObjectFactory>元素：

指定对象生成工厂类，用于将查询结果封装成对象返回。这是可选设置，若不指定，ibatis将使用Class.newInstance()的方式生成查询结果类。对象工厂类必须实现com.ibatis.sqlmap.engine.mapping.result.ResultObjectFactory接口。

<typeAlias>元素：

用来为一些亢长的类名起“别名”，例如：

<typeAlias alias="shortname" type="com.long.class.path.Class"/>

以后就能用“shortname”来取代“com.long.class.path.Class”了。

除了自己定义别名外，iBatis框架预先定义了一些别名，以方便使用，他们是：

Transaction Manager Aliases：

JDBC    com.ibatis.sqlmap.engine.transaction.jdbc.JdbcTransactionConfig

JTA     com.ibatis.sqlmap.engine.transaction.jta.JtaTransactionConfig

EXTERNAL com.ibatis.sqlmap.engine.transaction.external.ExternalTransactionConfig

Data Source Factory Aliases：

SIMPLE   com.ibatis.sqlmap.engine.datasource.SimpleDataSourceFactory

DBCP     com.ibatis.sqlmap.engine.datasource.DbcpDataSourceFactory

JNDI      com.ibatis.sqlmap.engine.datasource.JndiDataSourceFactory

<transactionManager>元素：

设置事务类型和<dataSource>元素，如上文所说，预定义的事务类型有JDBC, JTA, EXTERNAL；数据源类型有SIMPLE, DBCP, JNDI；若指定EXTERNAL或JTA，那就还有额外的属性需要设置：

 

<dataSource>元素：

在transactionManager元素中，定义数据源。预定义三种数据源工厂：SIMPLE, DBCP, JNDI，不过也可以自己写一个。

SIMPLE:在没有容器数据源支持的情况下使用的最简单的数据源实现，具体设置见刚才的例子。

DBCP:使用apache的DBCP数据源，ibatis框架对其直接提供支持，设置方法如下：

<transactionManager type="JDBC">

<dataSource type="DBCP">

<property name="driverClassName" value="${driver}"/>

<property name="url" value="${url}"/>

<property name="username" value="${username}"/>

<property name="password" value="${password}"/>

<!-- OPTIONAL PROPERTIES BELOW -->

<property name="maxActive" value="10"/>

<property name="maxIdle" value="5"/>

<property name="maxWait" value="60000"/>

<!-- Use of the validation query can be problematic.

If you have difficulty, try without it. -->

<property name="validationQuery" value="select * from ACCOUNT"/>

<property name="logAbandoned" value="false"/>

<property name="removeAbandoned" value="false"/>

<property name="removeAbandonedTimeout" value="50000"/>

<property name="Driver.DriverSpecificProperty" value="SomeValue"/>

</datasource>

</transactionManager>

所有的设置属性请参考：http://jakarta.apache.org/commons/dbcp/configuration.html

注：以‘Driver.’开头的属性会被加入到JDBC的属性中（有些JDBC需要）。

JNDI:指定配置的JNDI数据源。设置格式：

<transactionManager type="JDBC" >

<dataSource type="JNDI">

<property name="DataSource" value="java:comp/env/jdbc/jpetstore"/>

</dataSource>

</transactionManager>

上面只是使用普通的JDBC事务，但通常设置JNDI数据源更愿意用JTA全局事务：

<transactionManager type="JTA" >

<property name="UserTransaction" value="java:/comp/UserTransaction"/>

<dataSource type="JNDI">

<property name="DataSource" value="java:comp/env/jdbc/jpetstore"/>

</dataSource>

</transactionManager>

<sqlMap>元素：

用来包含SQL映射文件或另一个配置文件，以classpath或URL的形式：

<!-- CLASSPATH RESOURCES -->

<sqlMap resource="com/ibatis/examples/sql/Customer.xml" />

<sqlMap resource="com/ibatis/examples/sql/Account.xml" />

<sqlMap resource="com/ibatis/examples/sql/Product.xml" />

<!-- URL RESOURCES -->

<sqlMap url="file:///c:/config/Customer.xml " />

<sqlMap url="file:///c:/config/Account.xml " />

<sqlMap url="file:///c:/config/Product.xml" />