以下内容引用自http://wiki.jikexueyuan.com/project/spring/beans-auto-wiring/spring-autowiring-by-Constructor.html:
此模式与byType类似,但它适用于构造函数参数。Spring容器查看在XML配置文件中将autowire属性设置为构造方法的bean。然后,它尝试把它的构造函数的参数与配置文件中beans名称中的一个进行匹配和连线。如果找到匹配,它将注入这些bean。否则,bean将不会被连线。
例如,如果bean定义通过配置文件中的构造函数设置为autowire ,并且具有使用SpellChecker类型的参数之一的构造函数,则Spring会查找名为SpellChecker的bean定义,并使用它来设置构造函数的参数。当然,还可以使用<constructor-arg>标签连接剩余的参数。
例子:
pom.xml:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.jsoft.testspring</groupId> <artifactId>testautoconstructor</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>testautoconstructor</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <!-- Spring Core --> <!-- http://mvnrepository.com/artifact/org.springframework/spring-core --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>4.1.4.RELEASE</version> </dependency> <!-- Spring Context --> <!-- http://mvnrepository.com/artifact/org.springframework/spring-context --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>4.1.4.RELEASE</version> </dependency> </dependencies> </project>
SpellChecker.java:
package com.jsoft.testspring.testautoconstructor; public class SpellChecker { public SpellChecker(){ System.out.println("SpellChecker无参数构造函数初始化"); } public void checkSpelling(){ System.out.println("SpellChecker检查方法"); } }
TextEditor.java:
package com.jsoft.testspring.testautoconstructor; public class TextEditor { private SpellChecker spellChecker; private String name; public TextEditor(SpellChecker spellChecker, String name) { System.out.println("SpellChecker通过构造函数初始化"); this.spellChecker = spellChecker; this.name = name; } public void spellCheck() { this.spellChecker.checkSpelling(); } public void getName(){ System.out.println(this.name); } }
beans.xml:
<?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.xsd"> <bean id="spellChecker" class="com.jsoft.testspring.testautoconstructor.SpellChecker"></bean> <bean id="textEditor" class="com.jsoft.testspring.testautoconstructor.TextEditor" autowire="constructor"> <constructor-arg value="Hello World!"></constructor-arg> </bean> </beans>
修改之前的beans.xml:
<?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.xsd"> <bean id="spellChecker" class="com.jsoft.testspring.testautoconstructor.SpellChecker"></bean> <bean id="textEditor" class="com.jsoft.testspring.testautoconstructor.TextEditor"> <constructor-arg ref="spellChecker"></constructor-arg> <constructor-arg value="Hello World!"></constructor-arg> </bean> </beans>
App.java:
package com.jsoft.testspring.testautoconstructor; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; /** * Hello world! * */ public class App { public static void main( String[] args ) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); TextEditor textEditor = (TextEditor)applicationContext.getBean("textEditor"); textEditor.spellCheck(); textEditor.getName(); } }
运行结果:
测试工程:https://github.com/easonjim/5_java_example/tree/master/springtest/test11/testautoconstructor