Spring框架参考手册_5.0.0_中文版_Part II_3.4

3.4 依赖

3.4.1 依赖注入

public class SimpleMovieLister {

// the SimpleMovieLister has a dependency on a MovieFinder
private MovieFinder movieFinder;

// a constructor so that the Spring container can inject a MovieFinder
public SimpleMovieLister(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}

// business logic that actually uses the injected MovieFinder is omitted...

}

package x.y;

public class Foo {

public Foo(Bar bar, Baz baz) {
// ...
}

}

Bar

Baz

<constructor-arg/>

<beans>
<bean id="foo" class="x.y.Foo">
<constructor-arg ref="bar"/>
<constructor-arg ref="baz"/>
</bean>

<bean id="bar" class="x.y.Bar"/>

<bean id="baz" class="x.y.Baz"/>
</beans>

<value>true</value>

package examples;

public class ExampleBean {

// Number of years to calculate the Ultimate Answer
private int years;

// The Answer to Life, the Universe, and Everything
private String ultimateAnswer;

public ExampleBean(int years, String ultimateAnswer) {
this.years = years;
this.ultimateAnswer = ultimateAnswer;
}

}

type

<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg type="int" value="7500000"/>
<constructor-arg type="java.lang.String" value="42"/>
</bean>

index

<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg index="0" value="7500000"/>
<constructor-arg index="1" value="42"/>
</bean>

<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg name="years" value="7500000"/>
<constructor-arg name="ultimateAnswer" value="42"/>
</bean>

@ConstructorProperties

package examples;

public class ExampleBean {

// Fields omitted

@ConstructorProperties({"years", "ultimateAnswer"})
public ExampleBean(int years, String ultimateAnswer) {
this.years = years;
this.ultimateAnswer = ultimateAnswer;
}

}

public class SimpleMovieLister {

// the SimpleMovieLister has a dependency on the MovieFinder
private MovieFinder movieFinder;

// a setter method so that the Spring container can inject a MovieFinder
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}

// business logic that actually uses the injected MovieFinder is omitted...

}

ApplicationContext

BeanDefinition

PropertyEditor

@Component

@Controller

@Configuration

@Bean

@Required

JMX MBeans

ApplicationContext

ApplicationContext

BeanCurrentlyInCreationException

ApplicationContext

<bean id="exampleBean" class="examples.ExampleBean">
<!-- setter injection using the nested ref element -->
<property name="beanOne">
<ref bean="anotherExampleBean"/>
</property>

<!-- setter injection using the neater ref attribute -->
<property name="beanTwo" ref="yetAnotherBean"/>
<property name="integerProperty" value="1"/>
</bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/>
<bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

public class ExampleBean {

private AnotherBean beanOne;
private YetAnotherBean beanTwo;
private int i;

public void setBeanOne(AnotherBean beanOne) {
this.beanOne = beanOne;
}

public void setBeanTwo(YetAnotherBean beanTwo) {
this.beanTwo = beanTwo;
}

public void setIntegerProperty(int i) {
this.i = i;
}

}

<bean id="exampleBean" class="examples.ExampleBean">
<!-- constructor injection using the nested ref element -->
<constructor-arg>
<ref bean="anotherExampleBean"/>
</constructor-arg>

<!-- constructor injection using the neater ref attribute -->
<constructor-arg ref="yetAnotherBean"/>

<constructor-arg type="int" value="1"/>
</bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/>
<bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

public class ExampleBean {

private AnotherBean beanOne;
private YetAnotherBean beanTwo;
private int i;

public ExampleBean(
AnotherBean anotherBean, YetAnotherBean yetAnotherBean, int i) {
this.beanOne = anotherBean;
this.beanTwo = yetAnotherBean;
this.i = i;
}

}

ExampleBean

<bean id="exampleBean" class="examples.ExampleBean" factory-method="createInstance">
<constructor-arg ref="anotherExampleBean"/>
<constructor-arg ref="yetAnotherBean"/>
<constructor-arg value="1"/>
</bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/>
<bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

public class ExampleBean {

// a private constructor
private ExampleBean(...) {
...
}

// a static factory method; the arguments to this method can be
// considered the dependencies of the bean that is returned,
// regardless of how those arguments are actually used.
public static ExampleBean createInstance (
AnotherBean anotherBean, YetAnotherBean yetAnotherBean, int i) {

ExampleBean eb = new ExampleBean (...);
// some other operations...
return eb;
}

}

<constructor-arg/>

factory-bean

class

3.4.2 依赖和配置的细节

<property/>

<constructor-arg/>

<property/>

value

String

<bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<!-- results in a setDriverClassName(String) call -->
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mydb"/>
<property name="username" value="root"/>
<property name="password" value="masterkaoli"/>
</bean>

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> 
<bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close"
p:driverClassName="com.mysql.jdbc.Driver"
p:url="jdbc:mysql://localhost:3306/mydb"
p:username="root"
p:password="masterkaoli"/>

</beans>

IntelliJ IDEA

Spring Tool Suite (STS)

java.util.Properties

<bean id="mappings"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">

<!-- typed as a java.util.Properties -->
<property name="properties">
<value>
jdbc.driver.className=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mydb
</value>
</property>
</bean>

PropertyEditor

<value/>

java.util.Properties

<value/>

value

<constructor-arg/>

<property/>

idref

<bean id="theTargetBean" class="..."/>

<bean id="theClientBean" class="...">
<property name="targetName">
<idref bean="theTargetBean" />
</property>
</bean>

<bean id="theTargetBean" class="..." />

<bean id="client" class="...">
<property name="targetName" value="theTargetBean" />
</bean>

idref

client

targetName

client

client

idref

local

idref local

idref bean

<idref/>

ProxyFactoryBean

<idref/>

ref

<constructor-arg/>

<property/>

bean

local

parent

<ref/>

bean

bean

id

name

<ref bean="someBean"/>

parent

parent

id

name

parent

parent

<!-- in the parent context -->
<bean id="accountService" class="com.foo.SimpleAccountService">
<!-- insert dependencies as required as here -->
</bean>

<!-- in the child (descendant) context -->
<bean id="accountService" <!-- bean name is the same as the parent bean -->
class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="target">
<ref parent="accountService"/> <!-- notice how we refer to the parent bean -->
</property>
<!-- insert other configuration and dependencies as required here -->
</bean>

idref

local

idref local

idref bean

<property/>

<constructor-arg/>

<bean/>

<bean id="outer" class="...">
<!-- instead of using a reference to a target bean, simply define the target bean inline -->
<property name="target">
<bean class="com.example.Person"> <!-- this is the inner bean -->
<property name="name" value="Fiona Apple"/>
<property name="age" value="25"/>
</bean>
</property>
</bean>

scope

<list/>

<set/>

<map/>

<props/>

Collection

list

set

map

Properties

<bean id="moreComplexObject" class="example.ComplexObject">
<!-- results in a setAdminEmails(java.util.Properties) call -->
<property name="adminEmails">
<props>
<prop key="administrator">administrator@example.org</prop>
<prop key="support">support@example.org</prop>
<prop key="development">development@example.org</prop>
</props>
</property>
<!-- results in a setSomeList(java.util.List) call -->
<property name="someList">
<list>
<value>a list element followed by a reference</value>
<ref bean="myDataSource" />
</list>
</property>
<!-- results in a setSomeMap(java.util.Map) call -->
<property name="someMap">
<map>
<entry key="an entry" value="just some string"/>
<entry key ="a ref" value-ref="myDataSource"/>
</map>
</property>
<!-- results in a setSomeSet(java.util.Set) call -->
<property name="someSet">
<set>
<value>just some string</value>
<ref bean="myDataSource" />
</set>
</property>
</bean>

bean | ref | idref | list | set | map | props | value | null

<list/>

<map/>

<set/>

<props/>

<list/>

<map/>

<set/>

<props/>

<beans>
<bean id="parent" abstract="true" class="example.ComplexObject">
<property name="adminEmails">
<props>
<prop key="administrator">administrator@example.com</prop>
<prop key="support">support@example.com</prop>
</props>
</property>
</bean>
<bean id="child" parent="parent">
<property name="adminEmails">
<!-- the merge is specified on the child collection definition -->
<props merge="true">
<prop key="sales">sales@example.com</prop>
<prop key="support">support@example.co.uk</prop>
</props>
</property>
</bean>
<beans>

child

adminEmails

<props/>

merge=true

child

adminEmails

Properties

adminEmails

adminEmails

administrator=administrator@example.com
sales=sales@example.com
support=support@example.co.uk

Properties

<props/>

support

<list/>

<map/>

<set/>

<list/>

List

Map

Set

Properties

Map

Set

Properties

Map

List

Exception

merge

merge

Collection

String

Collection

Collection

Collection

public class Foo {

private Map<String, Float> accounts;

public void setAccounts(Map<String, Float> accounts) {
this.accounts = accounts;
}
}

<beans>
<bean id="foo" class="x.y.Foo">
<property name="accounts">
<map>
<entry key="one" value="9.99"/>
<entry key="two" value="2.75"/>
<entry key="six" value="3.99"/>
</map>
</property>
</bean>
</beans>

foo

accounts

Map<String, Float>

Float

9.99, 2.75

3.99

Float

Strings

String

<bean class="ExampleBean">
<property name="email" value=""/>
</bean>

exampleBean.setEmail("")

<null/>

null

<bean class="ExampleBean">
<property name="email">
<null/>
</property>
</bean>

exampleBean.setEmail(null)

<property/>

bean

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> 
<bean name="classic" class="com.example.ExampleBean">
<property name="email" value="foo@bar.com"/>
</bean>

<bean name="p-namespace" class="com.example.ExampleBean"
p:email="foo@bar.com"/>
</beans>

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> 
<bean name="john-classic" class="com.example.Person">
<property name="name" value="John Doe"/>
<property name="spouse" ref="jane"/>
</bean>

<bean name="john-modern"
class="com.example.Person"
p:name="John Doe"
p:spouse-ref="jane"/>

<bean name="jane" class="com.example.Person">
<property name="name" value="Jane Doe"/>
</bean>
</beans>

<property name="spouse" ref="jane"/>

john

jane

p:spouse-ref="jane"

john

jane

spouse

-ref

Ref

constructor-arg

c:

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:c="http://www.springframework.org/schema/c"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> 
<bean id="bar" class="x.y.Bar"/>
<bean id="baz" class="x.y.Baz"/>

<!-- traditional declaration -->
<bean id="foo" class="x.y.Foo">
<constructor-arg ref="bar"/>
<constructor-arg ref="baz"/>
<constructor-arg value="foo@bar.com"/>
</bean>

<!-- c-namespace declaration -->
<bean id="foo" class="x.y.Foo" c:bar-ref="bar" c:baz-ref="baz" c:email="foo@bar.com"/>

</beans>

c:

p:

<!-- c-namespace index declaration -->
<bean id="foo" class="x.y.Foo" c:_0-ref="bar" c:_1-ref="baz"/>

_

null

<bean id="foo" class="foo.Bar">
<property name="fred.bob.sammy" value="123" />
</bean>

foo

fred

fred

sammy

bob

sammy

sammy

123

foo

fred

fred

bob

null

NullPointerException

3.4.3 使用depends-on

<ref/>

depends-on

depends-on

<bean id="beanOne" class="ExampleBean" depends-on="manager"/>
<bean id="manager" class="ManagerBean" />

depends-on

<bean id="beanOne" class="ExampleBean" depends-on="manager,accountDao">
<property name="manager" ref="manager" />
</bean>

<bean id="manager" class="ManagerBean" />
<bean id="accountDao" class="x.y.jdbc.JdbcAccountDao" />

depends-on

depends-on

depends-on

3.4.4 延迟初始化beans

ApplicationContext

<bean/>

lazy-init

<bean id="lazy" class="com.foo.ExpensiveToCreateBean" lazy-init="true"/>
<bean name="not.lazy" class="com.foo.AnotherBean"/>

ApplicationContext

ApplicationContext

lazy

not.lazy

ApplicationContext

<beans/>

default-lazy-init

<beans default-lazy-init="true">
<!-- no beans will be pre-instantiated... -->
</beans>

3.4.5 自动注入协作bean

ApplicationContext

<bean/>

autowire

ref

master

setMaster(..)

master

byType

byType

byType

key

String

Maps

Maps

Maps

property

constructor-arg

Strings

Classes

Maps

autowire-candidate

false

<bean/>

primary

true

<bean/>

autowire-candidate

false

@Autowired

<beans/>

default-autowire-candidates

Repository

*Repository

autowire-candidate

true

false

3.4.6 方法注入

ApplicationContextAware

getBean("B")

// a class that uses a stateful Command-style class to perform some processing
package fiona.apple;

// Spring-API imports
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class CommandManager implements ApplicationContextAware {

private ApplicationContext applicationContext;

public Object process(Map commandState) {
// grab a new instance of the appropriate Command
Command command = createCommand();
// set the state on the (hopefully brand new) Command instance
command.setState(commandState);
return command.execute();
}

protected Command createCommand() {
// notice the Spring API dependency!
return this.applicationContext.getBean("command", Command.class);
}

public void setApplicationContext(
ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}

stub

@Bean

CommandManager

createCommand()

CommandManager

package fiona.apple;

// no more Spring imports!

public abstract class CommandManager {

public Object process(Object commandState) {
// grab a new instance of the appropriate Command interface
Command command = createCommand();
// set the state on the (hopefully brand new) Command instance
command.setState(commandState);
return command.execute();
}

// okay... but where is the implementation of this method?
protected abstract Command createCommand();
}

CommandManager

<public|protected> [abstract] <return-type> theMethodName(no-arguments);

<!-- a stateful bean deployed as a prototype (non-singleton) -->
<bean id="command" class="fiona.apple.AsyncCommand" scope="prototype">
<!-- inject dependencies here as required -->
</bean>

<!-- commandProcessor uses statefulCommandHelper -->
<bean id="commandManager" class="fiona.apple.CommandManager">
<lookup-method name="createCommand" bean="command"/>
</bean>

commandManager

command

createCommand()

command

command

ServiceLocatorFactoryBean

org.springframework.beans.factory.config

ServiceLocatorFactoryBean

ObjectFactoryCreatingFactoryBean

replaced-method

computeValue

public class MyValueCalculator {

public String computeValue(String input) {
// some real code...
}

// some other methods...

}

org.springframework.beans.factory.support.MethodReplacer

/**
* meant to be used to override the existing computeValue(String)
* implementation in MyValueCalculator
*/
public class ReplacementComputeValue implements MethodReplacer {

public Object reimplement(Object o, Method m, Object[] args) throws Throwable {
// get the input value, work with it, and return a computed result
String input = (String) args[0];
...
return ...;
}
}

<bean id="myValueCalculator" class="x.y.z.MyValueCalculator">
<!-- arbitrary method replacement -->
<replaced-method name="computeValue" replacer="replacementComputeValue">
<arg-type>String</arg-type>
</replaced-method>
</bean>

<bean id="replacementComputeValue" class="a.b.c.ReplacementComputeValue"/>

<replaced-method/>

<arg-type/>

java.lang.String

java.lang.String
String
Str