Java代碼實作依賴注入

配置檔案setting.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans>

</property>

</bean>

<list>

<value>windows</value>

</list>

<set>

</set>

<map>

<value>CHINA</value>

</entry>

<value>JAPAN</value>

<value>KOREA</value>

</map>

</beans>

依據setting.xml，這裡将建構兩個Person類的執行個體me和you：

Person.java

package com.zj.ioc.di.imp;

public class Person {

private String name;

private int age;

private float height;

public String getName() {return name;}

public void setName(String name) {this.name = name;}

public int getAge() {return age;}

public void setAge(int age) {this.age = age;}

public float getHeight() {return height;}

public void setHeight(float height) {this.height = height;}

}

緊接着，建構一個ListOne的執行個體myList：

ListOne.java

import java.util.List;

public class ListOne {

private List<String> msg;

public List<String> getMsg() {return msg;}

public void setMsg(List<String> msg) {this.msg = msg;}

緊接着，建構一個SetOne的執行個體mySet：

SetOne.java

import java.util.Set;

public class SetOne {

private Set<String> msg;

public Set<String> getMsg() {return msg;}

public void setMsg(Set<String> msg) {this.msg = msg;}

緊接着，建構一個MapOne的執行個體myMap：

MapOne.java

import java.util.Map;

public class MapOne {

private Map<String,String> msg;

public Map<String, String> getMsg() {return msg;}

public void setMsg(Map<String, String> msg) {this.msg = msg;}

最後建構一個Persons類的執行個體us，其中包含me和you兩個已經建構好的對象：

Persons.java

public class Persons {

private Person i;

private Person u;

public Person getI() {return i;}

public void setI(Person i) {this.i = i;}

public Person getU() {return u;}

public void setU(Person u) {this.u = u;}

主要的實作機制是(代碼BeanFactory.java以及工程見附件)，

1.通過一個HashMap儲存構造好的對象，key就是bean的id屬性，value就是這個對象；

private Map<String, Object> beanMap = new HashMap<String, Object>();

……

public Object getBean(String beanId) {

Object obj = beanMap.get(beanId);

return obj;

查詢時

BeanFactory factory = new BeanFactory();

factory.init("setting.xml");

Person p1 = (Person) factory.getBean("me");

2.init方法讀入配置檔案setting.xml，并直接定位到beans下的bean元素，并執行個體化一個ElementHandler對其處理。

public void init(String xmlUri) throws Exception {

SAXReader saxReader = new SAXReader();

File file = new File(xmlUri);

try {

saxReader.addHandler("/beans/bean", new BeanHandler());

saxReader.read(file);

} catch (DocumentException e) {

System.out.println(e.getMessage());

}

3.ElementHandler，dom4j的ElementHandler接口有兩個方法，一個是onStart()，它主要用于處理該元素的屬性以及動态增加新的Handler類；另一個是onEnd()，它主要用于獲得該元素的Text文本以及删除已添加的Handler。

BeanHandler

private class BeanHandler implements ElementHandler {

Object obj = null;

public void .Start(ElementPath path) {

Element beanElement = path.getCurrent();

Attribute classAttribute = beanElement.attribute("class");

Class<?> bean = null;

try {

bean = Class.forName(classAttribute.getText());

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

Field fields[] = bean.getDeclaredFields();

Map<String, Field> mapField = new HashMap<String, Field>();

for (Field field : fields)

mapField.put(field.getName(), field);

obj = bean.newInstance();

} catch (InstantiationException e) {

} catch (IllegalAccessException e) {

path.addHandler("property", new PropertyHandler(mapField, obj));

public void .End(ElementPath path) {

Attribute idAttribute = beanElement.attribute("id");

beanMap.put(idAttribute.getText(), obj);

path.removeHandler("property");

PropertyHandler

private class PropertyHandler implements ElementHandler {

Map<String, Field> mapField;

Object obj;

public PropertyHandler(Map<String, Field> mapField, Object obj) {

this.mapField = mapField;

this.obj = obj;

Element propertyElement = path.getCurrent();

Attribute nameAttribute = propertyElement.attribute("name");

path.addHandler("value", new ValueHandler(mapField, obj,

nameAttribute));

path.addHandler("list", new ListHandler(mapField, obj,

path.addHandler("set", new SetHandler(mapField, obj,

path.addHandler("map", new MapHandler(mapField, obj,

path.addHandler("ref", new RefHandler(mapField, obj,

path.removeHandler("value");

path.removeHandler("list");

path.removeHandler("set");

path.removeHandler("map");

path.removeHandler("ref");

根據setting.xml，我們可以得到各種注入元素的Handler類處理流程圖。

4. setFieldValue()基于反射機制和相應的類資訊得到Field的類型，并根據setting.xml設定它的值。

private void setFieldValue(Object obj, Field field, String value) {

String fieldType = field.getType().getSimpleName();

if (fieldType.equals("int"))

field.setInt(obj, new Integer(value));

else if (fieldType.equals("float"))

field.setFloat(obj, new Float(value));

else if (fieldType.equals("boolean"))

field.setBoolean(obj, new Boolean(value));

else if (fieldType.equals("char"))

field.setChar(obj, value.charAt(0));

else if (fieldType.equals("double"))

field.setDouble(obj, new Double(value));

else if (fieldType.equals("long"))

field.setLong(obj, new Long(value));

else

field.set(obj, value);

} catch (IllegalArgumentException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

private void setFieldValue(Object obj, Field field, List<String> value) {

field.set(obj, value);

5.測試

public static void main(String[] args) {

BeanFactory factory = new BeanFactory();

factory.init("setting.xml");

Person p1 = (Person) factory.getBean("me");

System.out.print(p1.getName() + " ");

System.out.print(p1.getAge() + " ");

System.out.println(p1.getHeight());

Person p2 = (Person) factory.getBean("you");

System.out.print(p2.getName() + " ");

System.out.print(p2.getAge() + " ");

System.out.println(p2.getHeight());

ListOne list = (ListOne) factory.getBean("myList");

System.out.println(list.getMsg());

SetOne set = (SetOne) factory.getBean("mySet");

System.out.println(set.getMsg());

MapOne map = (MapOne) factory.getBean("myMap");

System.out.println(map.getMsg());

Persons us = (Persons) factory.getBean("us");

System.out.println(us.getI());

System.out.println(us.getU());

} catch (Exception e) {

測試結果：

ZJ 26 1.78

Mary 27 1.66

[java, c, windows]

[cat, tom, dog]

{c=CHINA, j=JAPAN, k=KOREA}

com.zj.ioc.di.imp.Person@1a5ab41

com.zj.ioc.di.imp.Person@18e3e60

本文轉自zhangjunhd51CTO部落格，原文連結：http://blog.51cto.com/zhangjunhd/126545，如需轉載請自行聯系原作者

Java代碼實作依賴注入

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