java反射快速入门（二）

上一遍博文 , 简单介绍java 反射的常用接口,本遍博文, 我会结合项目开发的实际例子讲解下 java反射的使用

现在有个需求, 要将一个对象转换成xml格式, 或者将一串xml转换一个对象, 这时我们循序渐进, 先从最简单的入手

一： 方案①

场景 ： NBA球员信息描述, 实体类如下

package test.reflect2;import org.dom4j.Element;

public class UserXMLDO {
    
    private Long id;
    private String name;
    private String password;
    private Double height;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Double getHeight() {
        return height;
    }

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

现在要把传进来的一个userXMLDO对象转成一串xml 

public static String toStringXML(UserXMLDO userXMLDO) throws Exception {
        StringBuffer sb = new StringBuffer();
        sb.append("<UserInfo>");
        sb.append(genNodeXmlString("id", userXMLDO.getId()));
        sb.append(genNodeXmlString("name", userXMLDO.getName()));
        sb.append(genNodeXmlString("password", userXMLDO.getPassword()));
        sb.append(genNodeXmlString("height", userXMLDO.getHeight()));
        sb.append("</UserInfo>");
        return sb.toString();
    }
    private static String genNodeXmlString(String nodeName, Object value) {
        StringBuffer sb = new StringBuffer();
        sb.append("<");
        sb.append(nodeName);
        sb.append(">");
        sb.append(value);
        sb.append("</");
        sb.append(nodeName);
        sb.append(">");
        return sb.toString();
    }

再提供一个方法,将xml转成userXMLDO对象

public static UserXMLDO toUserXMLDO(String xml) throws Exception {
        UserXMLDO  userXMLDO = new UserXMLDO();
        Element rootElement = DocumentXmlHelper.read(xml).getRootElement();
        
        for(Iterator<?> it = rootElement.elementIterator("id"); it.hasNext();) {
            Element element = (Element) it.next();
            userXMLDO.setId(Long.valueOf(element.getText()));
        }
        
        for(Iterator<?> it = rootElement.elementIterator("name"); it.hasNext();) {
            Element element = (Element) it.next();
            userXMLDO.setName(element.getText());
        }
        
        for(Iterator<?> it = rootElement.elementIterator("password"); it.hasNext();) {
            Element element = (Element) it.next();
            userXMLDO.setPassword(element.getText());
        }
        
        for(Iterator<?> it = rootElement.elementIterator("height"); it.hasNext();) {
            Element element = (Element) it.next();
            userXMLDO.setHeight(Double.valueOf(element.getText()));
        }
        return userXMLDO;
    }

 

上面的方案一,是最容易的想法做法,但此做法显得有点简单粗暴 。比如我要给球员添加一个 体重 属性, 这时你会发现, 要同时修改两个方法

toStringXML()、toUserXMLDO() 的实现

修改如下 ：
　　
private Double weight;

toStringXML() ： sb.append(genNodeXmlString("weight", userXMLDO.getName()));

toUserXMLDO() ：

for(Iterator<?> it = rootElement.elementIterator("weight"); it.hasNext();) { 

　　Element element = (Element) it.next(); 
　　userXMLDO.setHeight(Double.valueOf(element.getText()));
}

添加1个属性,改起来还是可以接受, 添加2个属性,还是可以接受的、....... 再添加100个属性呢？不能接受了吧~

二： 方案② 用反射

添加类型枚举

 1 package test.reflect2;
 2 
 3 import java.util.HashMap;
 4 import java.util.Map;
 5 
 6 public enum NodeEnum {
 7 
 8     userName("name", String.class),
 9     password("password", String.class),
10     userId("id", Long.class),
11     height("height", Double.class),
12     ;
13 
14     NodeEnum(String name, Class<?> type) {
15         this.name = name;
16         this.type = type;
17     }
18 
19     public static Map<String, Class<?>> getNodeMap() {
20         Map<String, Class<?>> map = new HashMap<String, Class<?>>();
21         NodeEnum[] nodeEnums = NodeEnum.values();
22         for (NodeEnum ne : nodeEnums) {
23             map.put(ne.getName(), ne.getType());
24         }
25         return map;
26     }
27 
28     private String name;
29     
30     private Class<?> type;
31 
32     public String getName() {
33         return name;
34     }
35 
36     public void setName(String name) {
37         this.name = name;
38     }
39 
40     public Class<?> getType() {
41         return type;
42     }
43 
44     public void setType(Class<?> type) {
45         this.type = type;
46     }
47 
48 
49 }

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