Spring裝配構造方法

並不是每一個JavaBean都只有一個無參數的構造方法，如果一個JavaBean的構造方法的參數有一個或多個，就需要使用<constructor-reg>標籤來為這些構造方法設定相應的參數值。

ConstructorBean.java

package chapter22;public class ConstructorBean {    private String name;    private String message;    private int number;        public ConstructorBean(String name) {        super();        this.name = name;        System.out.println("ConstructorBean(String name) 建構函式被調用");    }    public ConstructorBean(String name, int number) {        super();        this.name = name;        this.number = number;        System.out.println("ConstructorBean(String name,int number) 建構函式被調用");    }    public ConstructorBean(String name, String message) {        super();        this.name = name;        this.message = message;        System.out.println("ConstructorBean(String name,String message) 建構函式被調用");    }        public String getName() {        return name;    }    public String getMessage() {        return message;    }    public int getNumber() {        return number;    }}

TestConstructorBean.java

package chapter22;import org.springframework.context.ApplicationContext;import org.springframework.context.support.FileSystemXmlApplicationContext;public class TestConstructorBean {    public static void main(String args[])    {        ApplicationContext ctx=new FileSystemXmlApplicationContext("src//ConstructorBean.xml");        //ApplicationContext ctx=new FileSystemXmlApplicationContext("src//a.xml");        ConstructorBean cb=(ConstructorBean)ctx.getBean("constructor1");        System.out.println(cb.getName());        System.out.println("--------------------------------");                cb=(ConstructorBean)ctx.getBean("constructor2");        System.out.println("name:"+cb.getName());        System.out.println("message:"+cb.getMessage());        System.out.println("number:"+cb.getNumber());        System.out.println("--------------------------------");        //指定        cb=(ConstructorBean)ctx.getBean("constructor3");        System.out.println("name:"+cb.getName());        System.out.println("message:"+cb.getMessage());        System.out.println("number:"+cb.getNumber());        System.out.println("--------------------------------");        //指定第二個參數類型為int型。這樣會匹配第2個建構函式。        cb=(ConstructorBean)ctx.getBean("constructor4");        System.out.println("name:"+cb.getName());        System.out.println("message:"+cb.getMessage());        System.out.println("number:"+cb.getNumber());        System.out.println("--------------------------------");        //通過使用<consturctor-arg>標籤的index屬性來改變傳遞參數的順序        cb=(ConstructorBean)ctx.getBean("constructor5");        System.out.println("name:"+cb.getName());        System.out.println("message:"+cb.getMessage());        System.out.println("number:"+cb.getNumber());    }    }

constructor.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"    xmlns:p="http://www.springframework.org/schema/p"    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><!--要使用第1個構造方法建立ConstructorBean對象非常簡單，Spring會自動尋找ConstructorBean類中只有一個參數的構造方法。-->    <bean id="constructor1" class="chapter22.ConstructorBean">        <constructor-arg>            <value>Michael</value></constructor-arg></bean>

<!--這裡第二個參數是20，一般認為Spring會自動匹配第二種方法。但是實現上確實調用了第3中方法。因為在Spring中搜尋Bean的構造方法時，會先將參數值當成String類型資料來看。-->    <bean id="constructor2" class="chapter22.ConstructorBean">        <constructor-arg>            <value>bill</value></constructor-arg>        <constructor-arg>            <value>20</value></constructor-arg></bean>

<!--這裡的第二個參數使用了類型限定，即指定第二個參數所對應的類型是int，因此Spring會匹配第2中方法。-->    <bean id="constructor3" class="chapter22.ConstructorBean">        <constructor-arg>            <value>bill</value></constructor-arg>        <constructor-arg type="int">            <value>20</value>        </constructor-arg></bean>

<!--預設情況下Spring匹配建構函式是按參數的順序匹配的。-->    <bean id="constructor4" class="chapter22.ConstructorBean">        <constructor-arg>            <value>bike</value></constructor-arg>        <constructor-arg>            <value>John</value>        </constructor-arg></bean>

<!--但是可以通過index屬性來表示構造方法參數的位置，從0開始。-->    <bean id="constructor5" class="chapter22.ConstructorBean">        <constructor-arg index="1">            <value>bike</value>        </constructor-arg>        <constructor-arg index="0">            <value>John</value>        </constructor-arg></bean></beans>

Spring裝配多個設定檔的方法

TestTwoConfigueFile.java

package chapter22;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.springframework.context.support.FileSystemXmlApplicationContext;public class TestTwoConfigueFile {    public static void main(String args[])    {        //使用FileSystemXmlApplicationContext        //ApplicationContext ctx=new FileSystemXmlApplicationContext(new String[]{"src//applicationContext.xml","src//ConstructorBean.xml"});        //使用ClassPathXmlApplicationContext        ApplicationContext ctx=new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml","ConstructorBean.xml"});        System.out.println("--------------------------------");        MyBean mb=(MyBean)ctx.getBean("myBean");        //System.out.println(mb.getHello());        System.out.println(mb.getHello().getGreeting());        System.out.println(mb.getStrName());        System.out.println("--------------------------------");        ConstructorBean cb=(ConstructorBean)ctx.getBean("constructor1");        System.out.println(cb.getName());    }}