Spring中使用byName实现Beans自动装配

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mb5fe18fed96438 2017-05-22 03:47:00

文章标签 java spring xml maven 文章分类 Java 后端开发

此模式通过属性名称来指定自动装配。Spring容器查看XML配置文件中auto-wire属性设置为byName的bean。然后，它尝试将其属性与配置文件中相同名称定义的bean进行匹配并连接。如果找到匹配，它将注入这些bean。否则，bean将不会被连线。

例如，如果一个bean定义在配置文件中设置为autowire="byName"，并且它包含一个spellChecker属性（即它有一个setSpellChecker(...)方法），则Spring会查找一个名为spellChecker的bean定义，并使用它设置属性。当然，还可以使用<property>标签连接剩余的属性。

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>testautowiringbyname</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>testautowiringbyname</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.testautowiringbyname;

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.testautowiringbyname;

public class TextEditor {
    private SpellChecker spellChecker;

    public void setSpellChecker(SpellChecker spellChecker){
        System.out.println("TextEditor通过setter初始化");
        this.spellChecker = spellChecker;
    }

    public void spellCheck() {
        this.spellChecker.checkSpelling();
    }

}

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.testautowiringbyname.SpellChecker"></bean>

    <bean id="textEditor" class="com.jsoft.testspring.testautowiringbyname.TextEditor" autowire="byName">
    </bean>

</beans>

变化之前的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.testautowiringbyname.SpellChecker"></bean>

    <bean id="textEditor" class="com.jsoft.testspring.testautowiringbyname.TextEditor">
        <property name="SpellChecker" ref="spellChecker"  />
    </bean>

</beans>

使用了自动装配类型byName去实现，省略了<property>属性。

App.java：

package com.jsoft.testspring.testautowiringbyname;

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();
    }
}