Java動態生成類以及動態添加屬性

有個技術實現需求：動態生成類，其中類中的屬性來自參數對象中的全部屬性以及來自參數對象properties文件。

那么技術實現支持：使用CGLib代理。

具體的實現步驟：

1.配置Maven文件：

 

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.journey</groupId>
    <artifactId>journey</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>cglib</groupId>
            <artifactId>cglib</artifactId>
            <version>2.2.2</version>
        </dependency>
    </dependencies>

</project>

2.封裝的cglib類

 

package com.journey;

import net.sf.cglib.beans.BeanGenerator;
import net.sf.cglib.beans.BeanMap;

import java.util.Iterator;
import java.util.Map;
import java.util.Set;

/**
 * Created by little_eleventh_wolf on 2017/11/18.
 */
public class DynamicBean {
    private Object object = null; //動態生成的類
    private BeanMap beanMap = null; //存放屬性名稱以及屬性的類型

    public DynamicBean() {
        super();
    }

    public DynamicBean(Map propertyMap) {
        this.object = generateBean(propertyMap);
        this.beanMap = BeanMap.create(this.object);
    }

    /**
     * @param propertyMap
     * @return
     */
    private Object generateBean(Map propertyMap) {
        BeanGenerator generator = new BeanGenerator();
        Set keySet = propertyMap.keySet();
        for(Iterator i = keySet.iterator(); i.hasNext(); ) {
            String key = (String) i.next();
            generator.addProperty(key, (Class) propertyMap.get(key));
        }
        return generator.create();
    }

    /**
     * 給bean屬性賦值
     * @param property 屬性名
     * @param value 值
     */
    public void setValue(Object property, Object value) {
        beanMap.put(property, value);
    }

    /**
     * 通過屬性名得到屬性值
     * @param property 屬性名
     * @return 值
     */
    public Object getValue(String property) {
        return beanMap.get(property);
    }

    /**
     * 得到該實體bean對象
     * @return
     */
    public Object getObject() {
        return this.object;
    }
}

3.需求的實現類：

 

package com.journey;

import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Properties;
import java.util.Set;

/**
 * Created by little_eleventh_wolf on 2017/11/18.
 */
public class ClassUtil {
    private String filePath = "/config/"; //配置文件路徑

    public String getFilePath() {
        return filePath;
    }

    public void setFilePath(String filePath) {
        this.filePath = filePath;
    }

    public Object dynamicClass(Object object) throws Exception {
        HashMap returnMap = new HashMap();
        HashMap typeMap = new HashMap();
        //讀取配置文件
        Properties prop = new Properties();
        String sourcepackage = object.getClass().getName();
        String classname = sourcepackage.substring(sourcepackage.lastIndexOf(".") + 1);
        InputStream in = ClassUtil.class.getResourceAsStream(filePath + classname + ".properties");
        prop.load(in);

        Set<String> keylist = prop.stringPropertyNames();

        Class type = object.getClass();
        BeanInfo beanInfo = Introspector.getBeanInfo(type);
        PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
        for(int i = 0; i < propertyDescriptors.length; i++) {
            PropertyDescriptor descriptor = propertyDescriptors[i];
            String propertyName = descriptor.getName();
            if(!propertyName.equals("class")) {
                Method readMethod = descriptor.getReadMethod();
                Object result = readMethod.invoke(object, new Object[0]);
                if(result != null) {
                    returnMap.put(propertyName, result);
                } else {
                    returnMap.put(propertyName, "");
                }
                typeMap.put(propertyName, descriptor.getPropertyType());
            }
        }
        //加載配置文件中的屬性
        Iterator<String> iterator = keylist.iterator();
        while(iterator.hasNext()) {
            String key = iterator.next();
            returnMap.put(key, prop.getProperty(key));
            typeMap.put(key, Class.forName("java.lang.String"));
        }
        //map轉換成實體對象
        DynamicBean bean = new DynamicBean(typeMap);
        //賦值
        Set keys = typeMap.keySet();
        for(Iterator it = keys.iterator(); it.hasNext(); ) {
            String key = (String) it.next();
            bean.setValue(key, returnMap.get(key));
        }
        Object obj = bean.getObject();
        return obj;
    }

    public static void main(String[] args) throws Exception {
        new ClassUtil().dynamicClass(new LeapRole()/*LeapRole是個普通類，未貼源碼*/);
    }
}

4.技術實現目的：前台框架表格數據源實際上就是帶有數據的實體，但是grid中數據的類型、以及是否可見、toolbar工具欄上的按鈕、是否分頁，是針對實體而言，所以目前把這些信息作為實體的配置文件。在展示頁面之前，讀取全部信息，轉為參數對象的完整對象。