To switch over from the DTD-style to the new XML Schema-style, you need to make the following change.
<!-- DTD-style -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN"
"http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
<!-- <bean/> definitions here -->
</beans>
The equivalent file in the XML Schema-style would be...
<!-- XML Schema-style -->
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<!-- <bean/> definitions here -->
</beans>
注意
The 'xsi:schemaLocation' fragment is not actually required,
but can be included to reference a local copy of a schema (which can be useful
during development).
The above Spring XML configuration fragment is can pretty much be considered
boilerplate; you can simply use this and continue to write <bean/>
definitions like you have always done. However, the entire point of switching over is to
take advantage of the new Spring 2.0 XML tags since they make configuration easier. The
section entitled 第 A.2.2 节 “The util schema” demonstrates how you can
start immediately by using some of the more common utility tags.
The rest of this chapter is devoted to showing examples of the new Spring XML Schema based configuration, with at least one example for every new tag. The format follows a before and after style, with a before snippet of XML showing the old (but still 100% legal and supported) style, followed immediately by an after example showing the equivalent in the new XML Schema-based style.
First up is coverage of the util tags. As the name
implies, the util tags deal with common, utility
configuration issues, such as configuring collections, referencing constants,
and suchlike.
To use the tags in the util schema, you need to have
the following preamble at the top of your Spring XML configuration file;
the emboldened text in the snippet below references the correct schema so that
the tags in the util namespace are available to you.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd">
<!-- <bean/> definitions here -->
</beans>
Before...
<bean id="..." class="...">
<property name="isolation">
<bean id="java.sql.Connection.TRANSACTION_SERIALIZABLE"
class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean" />
</property>
</bean>
The above configuration uses a Spring FactoryBean
implementation, the FieldRetrievingFactoryBean, to
set the value of the 'isolation' property on a bean
to the value of the 'java.sql.Connection.TRANSACTION_SERIALIZABLE'
constant. This is all well and good, but it is a tad verbose and (unneccessarily)
exposes Spring's internal plumbing to the end user.
The following XML Schema-based version is more concise and clearly expresses the developer's intent ('inject this constant value'), and it just reads better.
<bean id="..." class="...">
<property name="isolation">
<util:constant static-field="java.sql.Connection.TRANSACTION_SERIALIZABLE"/>
</property>
</bean>
FieldRetrievingFactoryBean
is a FactoryBean which retrieves a
static or non-static field value. It is typically
used for retrieving public static
final constants, which may then be used to set a
property value or constructor arg for another bean.
Find below an example which shows how a static field is exposed, by
using the staticField
property:
<bean id="myField"
class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean">
<property name="staticField" value="java.sql.Connection.TRANSACTION_SERIALIZABLE"/>
</bean>
There is also a convenience usage form where the static
field is specified as the bean name:
<bean id="java.sql.Connection.TRANSACTION_SERIALIZABLE"
class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean"/>
This does mean that there is no longer any choice in what the bean id is (so any other bean that refers to it will also have to use this longer name), but this form is very concise to define, and very convenient to use as an inner bean since the id doesn't have to be specified for the bean reference:
<bean id="..." class="...">
<property name="isolation">
<bean id="java.sql.Connection.TRANSACTION_SERIALIZABLE"
class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean" />
</property>
</bean>
It is also possible to access a non-static (instance) field of another bean,
as described in the API documentation for the
FieldRetrievingFactoryBean
class.
Injecting enum values into beans as either property or constructor arguments is very
easy to do in Spring, in that you don't actually have to do
anything or know anything about the Spring internals (or even about classes such
as the FieldRetrievingFactoryBean). Let's look at an example
to see how easy injecting an enum value is; consider this JDK 5 enum:
package javax.persistence;
public enum PersistenceContextType {
TRANSACTION,
EXTENDED
}
Now consider a setter of type PersistenceContextType:
package example;
public class Client {
private PersistenceContextType persistenceContextType;
public void setPersistenceContextType(PersistenceContextType type) {
this.persistenceContextType = type;
}
}
.. and the corresponding bean definition:
<bean class="example.Client">
<property name="persistenceContextType" value="TRANSACTION" />
</bean>
This works for classic type-safe emulated enums (on JDK 1.4 and JDK 1.3) as well; Spring will automatically attempt to match the string property value to a constant on the enum class.
Before...
<!-- target bean to be referenced by name --> <bean id="testBean" class="org.springframework.beans.TestBean" scope="prototype"> <property name="age" value="10"/> <property name="spouse"> <bean class="org.springframework.beans.TestBean"> <property name="age" value="11"/> </bean> </property> </bean> <!-- will result in 10, which is the value of property 'age' of bean 'testBean' --> <bean id="testBean.age" class="org.springframework.beans.factory.config.PropertyPathFactoryBean"/>
The above configuration uses a Spring FactoryBean
implementation, the PropertyPathFactoryBean, to
create a bean (of type int) called
'testBean.age' that has a value equal to the 'age'
property of the 'testBean' bean.
After...
<!-- target bean to be referenced by name --> <bean id="testBean" class="org.springframework.beans.TestBean" scope="prototype"> <property name="age" value="10"/> <property name="spouse"> <bean class="org.springframework.beans.TestBean"> <property name="age" value="11"/> </bean> </property> </bean> <!-- will result in 10, which is the value of property 'age' of bean 'testBean' --> <util:property-path id="name" path="testBean.age"/>
The value of the 'path' attribute of the
<property-path/> tag follows the form 'beanName.beanProperty'.
PropertyPathFactoryBean is a
FactoryBean that evaluates a property path on a given
target object. The target object can be specified directly or via a bean
name. This value may then be used in another bean definition as a property
value or constructor argument.
Here's an example where a path is used against another bean, by name:
// target bean to be referenced by name
<bean id="person" class="org.springframework.beans.TestBean" scope="prototype">
<property name="age" value="10"/>
<property name="spouse">
<bean class="org.springframework.beans.TestBean">
<property name="age" value="11"/>
</bean>
</property>
</bean>
// will result in 11, which is the value of property 'spouse.age' of bean 'person'
<bean id="theAge"
class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
<property name="targetBeanName" value="person"/>
<property name="propertyPath" value="spouse.age"/>
</bean>
In this example, a path is evaluated against an inner bean:
<!-- will result in 12, which is the value of property 'age' of the inner bean -->
<bean id="theAge"
class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
<property name="targetObject">
<bean class="org.springframework.beans.TestBean">
<property name="age" value="12"/>
</bean>
</property>
<property name="propertyPath" value="age"/>
</bean>
There is also a shortcut form, where the bean name is the property path.
<!-- will result in 10, which is the value of property 'age' of bean 'person' -->
<bean id="person.age"
class="org.springframework.beans.factory.config.PropertyPathFactoryBean"/>
This form does mean that there is no choice in the name of the bean. Any reference to it will also have to use the same id, which is the path. Of course, if used as an inner bean, there is no need to refer to it at all:
<bean id="..." class="...">
<property name="age">
<bean id="person.age"
class="org.springframework.beans.factory.config.PropertyPathFactoryBean"/>
</property>
</bean>
The result type may be specifically set in the actual definition. This is not necessary for most use cases, but can be of use for some. Please see the Javadocs for more info on this feature.
Before...
<!-- creates a java.util.Properties instance with values loaded from the supplied location -->
<bean id="jdbcConfiguration" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
<property name="location" value="classpath:com/foo/jdbc-production.properties"/>
</bean>
The above configuration uses a Spring FactoryBean
implementation, the PropertiesFactoryBean, to
instantiate a java.util.Properties instance with values loaded from
the supplied Resource location).
After...
<!-- creates a java.util.Properties instance with values loaded from the supplied location -->
<util:properties id="jdbcConfiguration" location="classpath:com/foo/jdbc-production.properties"/>
Before...
<!-- creates ajava.util.Listinstance with values loaded from the supplied'sourceList'--> <bean id="emails" class="org.springframework.beans.factory.config.ListFactoryBean"> <property name="sourceList"> <list> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> </list> </property> </bean>
The above configuration uses a Spring FactoryBean
implementation, the ListFactoryBean, to
create a java.util.List instance initialized
with values taken from the supplied 'sourceList'.
After...
<!-- creates ajava.util.Listinstance with values loaded from the supplied'sourceList'--> <util:list id="emails"> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> </util:list>
You can also explicitly control the exact type of List
that will be instantiated and populated via the use of the 'list-class'
attribute on the <util:list/> element. For example, if we
really need a java.util.LinkedList to be instantiated, we could
use the following configuration:
<util:list id="emails" list-class="java.util.LinkedList">
<value>[email protected]</value>
<value>[email protected]</value>
<value>[email protected]</value>
<value>d'[email protected]</value>
</util:list>
If no 'list-class' attribute is supplied, a
List implementation will be chosen by the container.
Finally, you can also control the merging behavior using the
'merge' attribute of the <util:list/>
element; collection merging is described in more detail in the section entitled
第 3.3.3.4.1 节 “集合合并”.
Before...
<!-- creates ajava.util.Mapinstance with values loaded from the supplied'sourceMap'--> <bean id="emails" class="org.springframework.beans.factory.config.MapFactoryBean"> <property name="sourceMap"> <map> <entry key="pechorin" value="[email protected]"/> <entry key="raskolnikov" value="[email protected]"/> <entry key="stavrogin" value="[email protected]"/> <entry key="porfiry" value="[email protected]"/> </map> </property> </bean>
The above configuration uses a Spring FactoryBean
implementation, the MapFactoryBean, to
create a java.util.Map instance initialized
with key-value pairs taken from the supplied 'sourceMap'.
After...
<!-- creates ajava.util.Mapinstance with values loaded from the supplied'sourceMap'--> <util:map id="emails"> <entry key="pechorin" value="[email protected]"/> <entry key="raskolnikov" value="[email protected]"/> <entry key="stavrogin" value="[email protected]"/> <entry key="porfiry" value="[email protected]"/> </util:map>
You can also explicitly control the exact type of Map
that will be instantiated and populated via the use of the 'map-class'
attribute on the <util:map/> element. For example, if we
really need a java.util.TreeMap to be instantiated, we could
use the following configuration:
<util:map id="emails" map-class="java.util.TreeMap">
<entry key="pechorin" value="[email protected]"/>
<entry key="raskolnikov" value="[email protected]"/>
<entry key="stavrogin" value="[email protected]"/>
<entry key="porfiry" value="[email protected]"/>
</util:map>
If no 'map-class' attribute is supplied, a
Map implementation will be chosen by the container.
Finally, you can also control the merging behavior using the
'merge' attribute of the <util:map/>
element; collection merging is described in more detail in the section entitled
第 3.3.3.4.1 节 “集合合并”.
Before...
<!-- creates ajava.util.Setinstance with values loaded from the supplied'sourceSet'--> <bean id="emails" class="org.springframework.beans.factory.config.SetFactoryBean"> <property name="sourceSet"> <set> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> </set> </property> </bean>
The above configuration uses a Spring FactoryBean
implementation, the SetFactoryBean, to
create a java.util.Set instance initialized
with values taken from the supplied 'sourceSet'.
After...
<!-- creates ajava.util.Setinstance with values loaded from the supplied'sourceSet'--> <util:set id="emails"> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> <value>[email protected]</value> </util:set>
You can also explicitly control the exact type of Set
that will be instantiated and populated via the use of the 'set-class'
attribute on the <util:set/> element. For example, if we
really need a java.util.TreeSet to be instantiated, we could
use the following configuration:
<util:set id="emails" set-class="java.util.TreeSet">
<value>[email protected]</value>
<value>[email protected]</value>
<value>[email protected]</value>
<value>[email protected]</value>
</util:set>
If no 'set-class' attribute is supplied, a
Set implementation will be chosen by the container.
Finally, you can also control the merging behavior using the
'merge' attribute of the <util:set/>
element; collection merging is described in more detail in the section entitled
第 3.3.3.4.1 节 “集合合并”.
The jee tags deal with JEE (Java Enterprise Edition)-related
configuration issues, such as looking up a JNDI object and defining EJB references.
To use the tags in the jee schema, you need to have
the following preamble at the top of your Spring XML configuration file;
the emboldened text in the following snippet references the correct schema so that
the tags in the jee namespace are available to you.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:jee="http://www.springframework.org/schema/jee"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-2.0.xsd">
<!-- <bean/> definitions here -->
</beans>
Before...
<bean id="simple" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="jdbc/MyDataSource"/>
</bean>
After...
<jee:jndi-lookup id="simple" jndi-name="jdbc/MyDataSource"/>
Before...
<bean id="simple" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="jdbc/MyDataSource"/>
<property name="jndiEnvironment">
<props>
<prop key="foo">bar</prop>
</props>
</property>
</bean>
After...
<jee:jndi-lookup id="simple" jndi-name="jdbc/MyDataSource">
<jee:environment>foo=bar</jee:environment>
</jee:jndi-lookup>
Before...
<bean id="simple" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="jdbc/MyDataSource"/>
<property name="jndiEnvironment">
<props>
<prop key="foo">bar</prop>
<prop key="ping">pong</prop>
</props>
</property>
</bean>
After...
<jee:jndi-lookup id="simple" jndi-name="jdbc/MyDataSource">
<!-- newline-separated, key-value pairs for the environment (standard Properties format) -->
<jee:environment>
foo=bar
ping=pong
</jee:environment>
</jee:jndi-lookup>
Before...
<bean id="simple" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="jdbc/MyDataSource"/>
<property name="cache" value="true"/>
<property name="resourceRef" value="true"/>
<property name="lookupOnStartup" value="false"/>
<property name="expectedType" value="com.myapp.DefaultFoo"/>
<property name="proxyInterface" value="com.myapp.Foo"/>
</bean>
After...
<jee:jndi-lookup id="simple"
jndi-name="jdbc/MyDataSource"
cache="true"
resource-ref="true"
lookup-on-startup="false"
expected-type="com.myapp.DefaultFoo"
proxy-interface="com.myapp.Foo"/>
The <jee:local-slsb/> tag configures a
reference to an EJB Stateless SessionBean.
Before...
<bean id="simple"
class="org.springframework.ejb.access.LocalStatelessSessionProxyFactoryBean">
<property name="jndiName" value="ejb/RentalServiceBean"/>
<property name="businessInterface" value="com.foo.service.RentalService"/>
</bean>
After...
<jee:local-slsb id="simpleSlsb" jndi-name="ejb/RentalServiceBean"
business-interface="com.foo.service.RentalService"/>
<bean id="complexLocalEjb"
class="org.springframework.ejb.access.LocalStatelessSessionProxyFactoryBean">
<property name="jndiName" value="ejb/RentalServiceBean"/>
<property name="businessInterface" value="com.foo.service.RentalService"/>
<property name="cacheHome" value="true"/>
<property name="lookupHomeOnStartup" value="true"/>
<property name="resourceRef" value="true"/>
</bean>
After...
<jee:local-slsb id="complexLocalEjb"
jndi-name="ejb/RentalServiceBean"
business-interface="com.foo.service.RentalService"
cache-home="true"
lookup-home-on-startup="true"
resource-ref="true">
The <jee:remote-slsb/> tag configures a
reference to a remote EJB Stateless SessionBean.
Before...
<bean id="complexRemoteEjb"
class="org.springframework.ejb.access.SimpleRemoteStatelessSessionProxyFactoryBean">
<property name="jndiName" value="ejb/MyRemoteBean"/>
<property name="businessInterface" value="com.foo.service.RentalService"/>
<property name="cacheHome" value="true"/>
<property name="lookupHomeOnStartup" value="true"/>
<property name="resourceRef" value="true"/>
<property name="homeInterface" value="com.foo.service.RentalService"/>
<property name="refreshHomeOnConnectFailure" value="true"/>
</bean>
After...
<jee:remote-slsb id="complexRemoteEjb"
jndi-name="ejb/MyRemoteBean"
business-interface="com.foo.service.RentalService"
cache-home="true"
lookup-home-on-startup="true"
resource-ref="true"
home-interface="com.foo.service.RentalService"
refresh-home-on-connect-failure="true">
The lang tags deal with exposing objects that have been
written in a dynamic language such as JRuby or Groovy as beans in the Spring
container.
These tags (and the dynamic language support) are comprehensively covered
in the chapter entitled 第 24 章 动态语言支持. Please do consult that
chapter for full details on this support and the lang tags
themselves.
In the interest of completeness, to use the tags in the lang
schema, you need to have the following preamble at the top of your Spring XML
configuration file; the emboldened text in the following snippet references the
correct schema so that the tags in the lang namespace are
available to you.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:lang="http://www.springframework.org/schema/lang"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-2.0.xsd">
<!-- <bean/> definitions here -->
</beans>
The tx tags deal with configuring all of those
beans in Spring's comprehensive support for transactions. These tags are
covered in the chapter entitled 第 9 章 事务管理.
提示
You are strongly encouraged to look at the
'spring-tx-2.0.xsd' file that ships with the Spring
distribution. This file is (of course), the XML Schema for Spring's
transaction configuration, and covers all of the various tags in the
tx namespace, including attribute defaults and
suchlike. This file is documented inline, and thus the information is
not repeated here in the interests of adhering to the DRY (Don't Repeat
Yourself) principle.
In the interest of completeness, to use the tags in the tx
schema, you need to have the following preamble at the top of your Spring XML
configuration file; the emboldened text in the following snippet references the
correct schema so that the tags in the tx namespace are
available to you.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
<!-- <bean/> definitions here -->
</beans>
注意
Often when using the tags in the tx namespace you will also be using
the tags from the aop namespace (since the declarative transaction support in Spring is implemented using
AOP). The above XML snippet contains the relevant lines needed to reference the aop schema
so that the tags in the aop namespace are available to you.
The aop tags deal with configuring all things
AOP in Spring: this includes Spring's own proxy-based AOP framework and Spring's
integration with the AspectJ AOP framework. These tags are
comprehensively covered in the chapter entitled 第 6 章 使用Spring进行面向切面编程（AOP）.
In the interest of completeness, to use the tags in the aop
schema, you need to have the following preamble at the top of your Spring XML
configuration file; the emboldened text in the following snippet references the
correct schema so that the tags in the aop namespace are
available to you.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
<!-- <bean/> definitions here -->
</beans>
The tool tags are for use when you want to add
tooling-specific metadata to your custom configuration elements. This metadata
can then be consumed by tools that are aware of this metadata, and the tools can
then do pretty much whatever they want with it (validation, etc.).
The tool tags are not documented in this release of
Spring as they are currently undergoing review. If you are a third party tool
vendor and you would like to contribute to this review process, then do mail
the Spring mailing list. The currently supported tool
tags can be found in the file 'spring-tool-2.0.xsd' in the
'src/org/springframework/beans/factory/xml' directory of the
Spring source distribution.
Last but not least we have the tags in the beans schema.
These are the same tags that have been in Spring since the very dawn of the framework.
Examples of the various tags in the beans schema are not shown here
because they are quite comprehensively covered in the section entitled 第 3.3.3 节 “bean属性及构造器参数详解”
(and indeed in that entire chapter).
One thing that is new to the beans tags themselves in Spring 2.0 is the idea
of arbitrary bean metadata. In Spring 2.0 it is now possible to add zero or more
key / value pairs to <bean/> XML definitions. What, if
anything, is done with this extra metadata is totally up to your own custom logic (and
so is typically only of use if you are writing your own custom tags as described in
the appendix entitled 附录 B, Extensible XML authoring).
Find below an example of the <meta/> tag in the context
of a surrounding <bean/> (please note that without any logic
to interpret it said metadata is effectively useless as-is).
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<bean id="foo" class="x.y.Foo">
<meta key="cacheName" value="foo"/>
<property name="name" value="Rick"/>
</bean>
</beans>
In the case of the above example, you would assume that there is some logic that will consume the bean definition and set up some caching infrastructure using the supplied metadata.