spring注入

 IOC容器的对象实例化是通过配置文件来实现的。术语上这叫做注入。注入有两种形式，采用构造方法注入和采用setter注入。具体的注入形式如下

**************构造方法方式*******************

UserManagerImpl类：

 

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;
    }


}

 

配置文件代码：

 

<?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类：

 

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;
    }

}

 

配置文件代码：

 

<?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>

 

比较：

1.构造方法：

对于依赖关系无须变化的Bean，构造注入更有用处；因为没有setter方法，所有的依赖关系全部在构造器内设定，因此，不用担心后续代码对依赖关系的破坏。依赖关系只能在构造器中设定，则只有组件的创建者才能改变组件的依赖关系。对组件的调用者而言，组件内部的依赖关系完全透明，更符合高内聚的原则。

构造注入可以在构造器中决定依赖关系的注入顺序。

2，setter方法：

与传统的JavaBean的写法更相似，程序员更容易理解、接受，通过setter方式设定依赖关系显得更加直观、明显；对于复杂的依赖关系，如果采用构造注入，会导致构造器过于臃肿，难以阅读。Spring在创建Bean实例时，需要同时实例化其依赖的全部实例，因而导致死你功能下降。而使用设置注入，则避免这下问题；尤其在某些属性可选的情况下，多参数的构造器更加笨拙。

【属性编辑器】

Spring内置了一些属性编辑器，可以将一些普通常用的属性注入，将Spring配置文件中的String类型转换成相应的Java对象。例如一个类里面的一个整型属性，在配置文件中我们是通过String类型的数字直接进行配置即可。如下示例：

Bean1类：

 

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>

 

测试方法：

 

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());
    }

}

 

【自定义属性编辑器】

Spring具有多个自定义编辑器，它们能够自动把注入的String值转化为更复杂的类型。例如Date类型，如果直接按照上面实例的方式进行配置，就会报错如下：

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';

因为Spring没有内置Date的属性编辑器，需要我们自己创建。创建过程：

1.编写UtilDatePropertyEditor类，继承PropertyEditorSupport，覆盖setAsText()方法，其中text参数就是配置文件中的值。我们的任务就是把text转换成date类型的值。

 

package com.bjpowernode.spring;

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

/**
 * java.util.Date属性编辑器
 * @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.将自定义的属性编辑器注入到spring中，为了方便管理我们再新建一个配置文件applicationContext-editor.xml（测试时记得将该配置文件一同加载即可）

 

<?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>