spring注入

 IOC容器的對象實例化是經過配置文件來實現的。術語上這叫作注入。注入有兩種形式，採用構造方法注入和採用setter注入。具體的注入形式以下

**************構造方法方式*******************

UserManagerImpl類：

 

package com.bjpowernode.spring.manager;

import com.bjpowernode.spring.dao.UserDao;

public class UserManagerImpl implements UserManager {

    private UserDao userDao;

    public UserManagerImpl(UserDao userDao) {
        this.userDao = userDao;
    }


}

 

配置文件代碼：

 

<?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/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">

    <bean id="userDao4Mysql" class="com.bjpowernode.spring.dao.UserDao4MySqlImpl" />

    <bean id="userManager" class="com.bjpowernode.spring.manager.UserManagerImpl">
        <constructor-arg ref="userDao4Mysql" />
    </bean>
</beans>

 

****************setter方式*****************

UserManagerImpl類：

 

package com.bjpowernode.spring.manager;

import com.bjpowernode.spring.dao.UserDao;

public class UserManagerImpl implements UserManager {

    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

}

 

配置文件代碼：

 

<?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/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">

    <bean id="userDao4Mysql" class="com.bjpowernode.spring.dao.UserDao4MySqlImpl" />

    <bean id="userManager" class="com.bjpowernode.spring.manager.UserManagerImpl">
<!--         <constructor-arg ref="userDao4Mysql" /> -->
        <property name="userDao" ref="userDao4Mysql" />
    </bean>
</beans>

 

比較：

1.構造方法：

對於依賴關係無須變化的Bean，構造注入更有用處；由於沒有setter方法，全部的依賴關係所有在構造器內設定，所以，不用擔憂後續代碼對依賴關係的破壞。依賴關係只能在構造器中設定，則只有組件的建立者才能改變組件的依賴關係。對組件的調用者而言，組件內部的依賴關係徹底透明，更符合高內聚的原則。

構造注入能夠在構造器中決定依賴關係的注入順序。

2，setter方法：

與傳統的JavaBean的寫法更類似，程序員更容易理解、接受，經過setter方式設定依賴關係顯得更加直觀、明顯；對於複雜的依賴關係，若是採用構造注入，會致使構造器過於臃腫，難以閱讀。Spring在建立Bean實例時，須要同時實例化其依賴的所有實例，於是致使死你功能降低。而使用設置注入，則避免這下問題；尤爲在某些屬性可選的狀況下，多參數的構造器更加笨拙。

【屬性編輯器】

Spring內置了一些屬性編輯器，能夠將一些普一般用的屬性注入，將Spring配置文件中的String類型轉換成相應的Java對象。例如一個類裏面的一個整型屬性，在配置文件中咱們是經過String類型的數字直接進行配置便可。以下示例：

Bean1類：

 

package com.bjpowernode.spring;

import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class Bean1 {

    private String strValue;

    private int intValue;

    private List listValue;

    private Set setValue;

    private String[] arrayValue;

    private Map mapValue;

    private Date dateValue;

    //get和set略


}

 

配置文件：

 

<?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/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd"
    default-lazy-init="true">
    <bean id="bean1" class="com.bjpowernode.spring.Bean1">
        <property name="strValue" value="Hello_Spring" />

        <!-- <property name="intValue" value="123"/> -->
        <property name="intValue">
            <value>123</value>
        </property>

        <property name="listValue">
            <list>
                <value>list1</value>
                <value>list2</value>
            </list>
        </property>
        <property name="setValue">
            <set>
                <value>set1</value>
                <value>set2</value>
            </set>
        </property>
        <property name="arrayValue">
            <list>
                <value>array1</value>
                <value>array2</value>
            </list>
        </property>
        <property name="mapValue">
            <map>
                <entry key="k1" value="v1" />
                <entry key="k2" value="v2" />
            </map>
        </property>
    </bean>

</beans>

 

測試方法：

 

package test;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.bjpowernode.spring.Bean1;

import junit.framework.TestCase;

public class InjectionTest extends TestCase {

    private BeanFactory factory;

    @Override
    protected void setUp() throws Exception {
        String[] configLocations = new String[] {
                "applicationContext-beans.xml"};

        factory = new ClassPathXmlApplicationContext(configLocations);
    }

    @Override
    protected void tearDown() throws Exception {

    }

    public void testInjection1() {
        Bean1 bean1 = (Bean1) factory.getBean("bean1");
        System.out.println("bean1.strValue=" + bean1.getStrValue());
        System.out.println("bean1.intValue=" + bean1.getIntValue());
        System.out.println("bean1.listValue=" + bean1.getListValue());
        System.out.println("bean1.setValue=" + bean1.getSetValue());
        System.out.println("bean1.arrayValue=" + bean1.getArrayValue());
        System.out.println("bean1.mapValue=" + bean1.getMapValue());
        System.out.println("bean1.dateValue=" + bean1.getDateValue());
    }

}

 

【自定義屬性編輯器】

Spring具備多個自定義編輯器，它們可以自動把注入的String值轉化爲更復雜的類型。例如Date類型，若是直接按照上面實例的方式進行配置，就會報錯以下：

org.springframework.beans.factory.BeanCreationException:Error creating bean with name 'bean' defined in class path resource[applicationContext.xml]: Initialization of bean failed; nested exception isorg.springframework.beans.TypeMismatchException: Failed to convert propertyvalue of type [java.lang.String] to required type [java.util.Date] for property'date';

由於Spring沒有內置Date的屬性編輯器，須要咱們本身建立。建立過程：

1.編寫UtilDatePropertyEditor類，繼承PropertyEditorSupport，覆蓋setAsText()方法，其中text參數就是配置文件中的值。咱們的任務就是把text轉換成date類型的值。

 

package com.bjpowernode.spring;

import java.beans.PropertyEditorSupport;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * java.util.Date屬性編輯器
 * @author Administrator
 *
 */
public class UtilDatePropertyEditor extends PropertyEditorSupport {

    private String pattern;

    @Override
    public void setAsText(String text) throws IllegalArgumentException {
        System.out.println("---UtilDatePropertyEditor.setAsText()--->" + text);
        try {
            Date date = new SimpleDateFormat(pattern).parse(text);
            this.setValue(date);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            throw new IllegalArgumentException(text);
        }
    }

    public void setPattern(String pattern) {
        this.pattern = pattern;
    }


}

 

2.將自定義的屬性編輯器注入到spring中，爲了方便管理咱們再新建一個配置文件applicationContext-editor.xml（測試時記得將該配置文件一同加載便可）

 

<?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/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">
    <bean id="customEditors" class="org.springframework.beans.factory.config.CustomEditorConfigurer">
        <property name="customEditors">
            <map>
                <entry key="java.util.Date">
                    <bean class="com.bjpowernode.spring.UtilDatePropertyEditor">
                        <property name="pattern" value="yyyy年MM月dd日"/>
                    </bean>
                </entry>
            </map>
        </property>
    </bean>
</beans>