spring ioc 模擬

 本文主要的內容就是用本身的代碼實現spring下面的代碼功能:

    InputStream is = new FileInputStream("bean.xml"); 

    XmlBeanFactory factory = new XmlBeanFactory(is); 

    Action action = (Action) factory.getBean("TheAction");

具體流程以下圖：

 

 

 1. 肯定有兩個類，一個是Course，一個是Student，Course由名稱、學分、描述組成。Student由學號、名字、課程組成。如今要先建一個Course而後把這個類做爲Student的Course屬性。

//Course.java：
package entity;
public class Course {
    private String name;
    private long credit;
    private String desc;
     public Course() {
        super();
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public long getCredit() {
        return credit;
    }
    public void setCredit(long credit) {
        this.credit = credit;
    }
    public String getDesc() {
        return desc;
    }
    public void setDesc(String desc) {
        this.desc = desc;
    }

}

 

//Student.java：
package entity;
public class Student {
    private String NO;
    private String name;
    private Course course;
    public String getNO() {
        return NO;
    }
    public void setNO(String nO) {
        NO = nO;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Course getCourse() {
        return course;
    }
    public void setCourse(Course course) {
        this.course = course;
    }

}

 

2 在bean.xml中寫上bean的信息，我改了一下xml的名字，如今是conf.xml，name和class都是必要的，而children節點的property就是這個bean的一些屬性。property中的param指這個屬性的名字，text的部分是value。

 

<?xml version="1.0" encoding="UTF-8"?>
<beans>
<bean id="mathCourse" class="entity.Course">
    <property param="name">math</property>
    <property param="credit">5</property>
    <property param="desc">
        數學
    </property>
</bean>
<bean id="stud0" class="entity.Student">
    <property param="NO">000</property>
    <property param="name">stud0</property>
    <property param="course" ref="mathCourse">mathCourse</property>
</bean>
</beans>

xml裏面的信息要和上面的類的屬性相互對應，在property上寫有ref的節點說明是根據上上面已經定義的bean注入進來的。

 

 

 

3.用一個Property類做爲存放每一個<property/>節點的信息，由於比較的簡單，因此這個類只有幾個屬性

 

package entity;
public class Property {
    private String name;
    private boolean ref;
    private String value;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public boolean isRef() {
        return ref;
    }
    public void setRef(boolean ref) {
        this.ref = ref;
    }
    public String getValue() {
        return value;
    }
    public void setValue(String value) {
        this.value = value;
    }
}

 

 

4.經過解析這個xml得到寫在裏面的信息。這裏使用dom4j

 

public static Map<String, Property> getBeanParams(Element bean) {
        Map<String, Property> map = new HashMap<String, Property>();
        for (Iterator<Element> beanIt = bean.elementIterator(); beanIt
                .hasNext();) {
            Element property = beanIt.next();
            Property p = new Property();
            p.setName(property.attribute("param").getStringValue());
            p.setRef(property.attribute("ref") == null ? false : true);
            p.setValue(property.getTextTrim());
            map.put(property.attribute("param").getStringValue(), p);
        }
        return map;
    }

 

 

5.使用java的反射對對象的屬性進行賦值。能夠經過兩種方法，一種是直接經過訪問屬性，另外一種就是使用方法就是setXXX(value)，固然也能夠用構造函數，用起來不是通常的麻煩。

 

package reflect;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
public class ClassHelper {
    // 經過類方法獲取屬性值

public static Map<String, Object> getMethods(Object obj)
            throws IllegalAccessException, IllegalArgumentException,
            InvocationTargetException {
        Map<String, Object> map = new HashMap<String, Object>();
        Method[] method = obj.getClass().getDeclaredMethods();
        for (int i = 0; i < method.length; i++) {
            String methodName = method[i].getName().toString();
            if (methodName.startsWith("get")) {
                map.put(method[i].getName().toString(),
                        method[i].invoke(obj, null));
            }
        }
        return map;
    }
    // 經過類方法對屬性賦值
    public static String[] setMethods(Object obj,
            Map<String, Property> propertyMap, Map<String, Object> objMap)
            throws NumberFormatException, IllegalAccessException,
            IllegalArgumentException, InvocationTargetException {
        Method[] method = obj.getClass().getDeclaredMethods();
        String[] methods = new String[method.length];
        for (int i = 0; i < method.length; i++) {
            String methodName = method[i].getName().toString();
            if (methodName.startsWith("set")) {
                for (Class<?> c : method[i].getParameterTypes()) {
                    String paramType = c.getSimpleName().toString();// 獲取方法中變量的類型
                    String name = method[i].getName().toString()
                            .substring(3, methodName.length()).toLowerCase();// 記得要轉換爲小寫，截取後獲得的string開頭字母是大寫
                    // System.out.println(name);
                    Property property = propertyMap.get(name);
                    String val = property.getValue();
                    if (property.isRef()) {
                        Object o = objMap.get(val);
                        method[i].invoke(obj, o);
                    } else if (paramType.toLowerCase().equals("long")) {
                        method[i].invoke(obj, Long.parseLong(val));
                    } else if (paramType.toLowerCase().equals("int")
                            || paramType.equals("Integer")) {
                        method[i].invoke(obj, Integer.valueOf(val));
                    } else if (paramType.toLowerCase().equals("float")) {
                        method[i].invoke(obj, Float.valueOf(val));
                    } else if (paramType.toLowerCase().equals("short")) {
                        method[i].invoke(obj, Short.valueOf(val));
                    } else if (paramType.toLowerCase().equals("double")) {
                        method[i].invoke(obj, Double.valueOf(val));
                    } else if (paramType.toLowerCase().equals("char")) {
                        method[i].invoke(obj, val.charAt(0));
                    } else if (paramType.toLowerCase().equals("boolean")) {
                        method[i].invoke(obj, Boolean.valueOf(val));
                    } else if (paramType.toLowerCase().equals("byte")) {
                        method[i].invoke(obj, val.getBytes()[0]);
                    } else {
                            method[i].invoke(obj, val);
                    }
                }
            }
        }
        return methods;
    }
    // 獲取類屬性的值
    public static Map<String, Object> getFieldsValues(Object obj)
            throws IllegalArgumentException, IllegalAccessException {
        Field[] field = obj.getClass().getDeclaredFields();
        Map<String, Object> map = new HashMap<String, Object>();
        for (int i = 0; i < field.length; i++) {
            field[i].setAccessible(true); // 容許訪問私有屬性
            map.put(field[i].getName(), field[i].get(obj));// 使用屬性的名稱做爲key
                                                            // ，屬性的值做爲value
        }
        return map;
    }
    // 經過屬性直接賦值
    public static String[] setFields(Object obj,
            Map<String, Property> propertyMap, Map<String, Object> objMap)
            throws NumberFormatException, IllegalArgumentException,
            IllegalAccessException {
        Field[] field = obj.getClass().getDeclaredFields();
        String[] fields = new String[field.length];
        for (int i = 0; i < field.length; i++) {
            field[i].setAccessible(true); // 容許訪問私有屬性
            String name = field[i].getName();
            fields[i] = name;
            String type = field[i].getType().getSimpleName();
            // System.out.println("name:" + name + "   type:" + type);
            Property property = propertyMap.get(name);
            String val = property.getValue();
            if (property.isRef()) {
                Object o = objMap.get(val);
                field[i].set(obj, o);
            } else if (type.toLowerCase().equals("long")) {
                field[i].setLong(obj, Long.parseLong(val));
            } else if (type.toLowerCase().equals("int")
                    || type.equals("Integer")) {
                field[i].setInt(obj, Integer.valueOf(val));
            } else if (type.toLowerCase().equals("float")) {
                field[i].setFloat(obj, Float.valueOf(val));
            } else if (type.toLowerCase().equals("short")) {
                field[i].setShort(obj, Short.valueOf(val));
            } else if (type.toLowerCase().equals("double")) {
                field[i].setDouble(obj, Double.valueOf(val));
            } else if (type.toLowerCase().equals("char")) {
                field[i].setChar(obj, val.charAt(0));
            } else if (type.toLowerCase().equals("boolean")) {
                field[i].setBoolean(obj, Boolean.valueOf(val));
            } else if (type.toLowerCase().equals("byte")) {
                field[i].setByte(obj, val.getBytes()[0]);
            } else {
                // System.out.println(val);
                field[i].set(obj, val);
            }
        }
        return fields;
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
    }
}

 

 

5.利用上面的方法構建BeanFactory；

 

public class BeanFactory {
    /**
     * @param args
     */
    private String path;
    public static Map<String, Object> map;
    public BeanFactory() {
        this("src/bean.xml");
    }
    public BeanFactory(String path) {
        super();
        this.path = path;
        init();
    }
    private void init() {
        Document doc = null;
        map = new HashMap<String, Object>();
        SAXReader reader = new SAXReader();
        try {
            doc = reader.read(new File(path));
            Element root = doc.getRootElement();
            for (Iterator<Element> beans = root.elementIterator(); beans
                    .hasNext();) {
                Element bean = beans.next();
                Map<String, String> beanParams = XmlHelper.getBeanParams(bean);
                Class cla = Class.forName(bean.attributeValue("class"));
                Object obj = cla.newInstance();
                // set value
                ClassHelper.setFields(obj, beanParams, map);
                // ClassHelper.setMethods(obj, beanParams, map);
                map.put(bean.attributeValue("name"), obj);
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        // System.out.println(System.getProperty("user.dir"));
    }
    public static <T> T getBean(String key, Class<T> classOf) {
        return (T) map.get(key);
    }

    public String getPath() {
        return path;
    }
    public void setPath(String path) {
        this.path = path;
    }
}

 

 

本次實現是經過直接訪問類的屬性進行賦值的。

6.寫個main函數做爲測試；

 

public class Main {
    /**
     * @param args
     * @throws InvocationTargetException
     * @throws IllegalArgumentException
     * @throws IllegalAccessException
     */
    public static void main(String[] args) throws IllegalAccessException,
            IllegalArgumentException, InvocationTargetException {
        // TODO Auto-generated method stub
        BeanFactory beanFactory = new BeanFactory("src/conf.xml");
        Student stud0 = BeanFactory.getBean("stud0", Student.class);
        Course mathCourse = BeanFactory.getBean("mathCourse", Course.class);
        System.out.println("stud name:" + stud0.getName());
        System.out.println("stud NO.:" + stud0.getNO());
        Course testMathCourse = stud0.getCourse();
        System.out.println("the same ?:"
                + (mathCourse == testMathCourse ? true : false));
        System.out.println("math name:" + mathCourse.getName());
        System.out.println("math credit:" + mathCourse.getCredit());
        System.out.println("math desc:" + mathCourse.getDesc());
        Map<String, Object> vals = ClassHelper.getMethods(stud0);
        for (Iterator<String> it = vals.keySet().iterator(); it.hasNext();) {
            String key=it.next();
            System.out.println(key+":"+vals.get(key));
        }
    }
}

 

 

7.運行結果；

stud name:stud0

stud NO.:000

the same ?:true

math name:math

math credit:5

math desc:數學

getNO:000

getCourse:entity.Course@db95a1

getName:stud0

經過第三行的輸出能夠看出來，stud0的Course和從BeanFactory拿出來的是同一個對象。其餘的值和xml設置的值是一個樣的。

 InputStream is = new FileInputStream("bean.xml"); 

    XmlBeanFactory factory = new XmlBeanFactory(is); 

BeanFactory beanFactory = new BeanFactory("src/conf.xml");此句和上面的兩句功能同樣

Action action = (Action) factory.getBean("TheAction");

Student stud0 = BeanFactory.getBean("stud0", Student.class);此 句和上一句功能同樣。

在此目的達成。

done.

 

source code url:

https://github.com/scalaview/reflection