J2EE常用工具类—Value Object工具类

package cn.org.jshuwei.j2ee.util;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.Map;

/**
* Value Object工具类<br>
* 使用实例：<br>
* 
* <pre>
* Person类：
* package cn.org.jshuwei.j2ee.util.test;
* 
* public class Person {
*     private String id;
*     private User u;
* 
*     public Person(String id, User u) {
*         super();
*         this.id = id;
*         this.u = u;
*     }
* 
*     public String getId() {
*         return id;
*     }
* 
*     public void setId(String id) {
*         this.id = id;
*     }
* 
*     public User getU() {
*         return u;
*     }
* 
*     public void setU(User u) {
*         this.u = u;
*     }
* 
* }
* User类：
* package cn.org.jshuwei.j2ee.util.test;
* 
* public class User {
*     private String userName;
*     private String userPass;
*     private Integer userAge;
*     
*     public User(){
*         
*     }
*     
*     public User(String userName, String userPass, int userAge) {
*         super();
*         this.userName = userName;
*         this.userPass = userPass;
*         this.userAge = userAge;
*     }
*     
*     public String getUserName() {
*         return userName;
*     }
*     public void setUserName(String userName) {
*         this.userName = userName;
*     }
*     public String getUserPass() {
*         return userPass;
*     }
*     public void setUserPass(String userPass) {
*         this.userPass = userPass;
*     }
*     public Integer getUserAge() {
*         return userAge;
*     }
*     public void setUserAge(Integer userAge) {
*         this.userAge = userAge;
*     }
* }
* 测试调用类：
* package cn.org.jshuwei.j2ee.util.test;
* 
* import java.util.Map;
* 
* import cn.org.jshuwei.j2ee.util.VOUtils;
* 
* public class Test {
* 
*     public static void main(String[] args) {
*         User u = new User("huwei","123",23);
*         Person p = new Person("1",u);
*         Map<String,Object> map = VOUtils.beanToMap(p,"cn.org.jshuwei.j2ee.util.test"); 
*         for(Map.Entry<String, Object> entry : map.entrySet()){   
*             String value = entry.getValue().toString();   
*             String key = entry.getKey();
*             System.out.println(key+"----"+value);
*         }
*         u = new User();
*         u.setUserName("jshuwei");
*         System.out.println(VOUtils.beanToWhereSql(u));
*     }    
* }
* </pre>
* 
* @author huwei(jshuwei.org.cn)
* 
*/
public class VOUtils {
    /**
     * 将实体类对象的属性值转换成属性名为key，属性值为value的Map<String,String>并返回
     * 
     * @param entity
     *            需要转换的实体类对象
     * @return 转换后的Map<String,String>
     */
    @SuppressWarnings("unchecked")
    public static Map<String, String> beanToMap(Object entity) {
        Class c = entity.getClass();
        Object fieldValue = null;
        String fieldName = null;
        Field[] fields = c.getDeclaredFields();
        Map<String, String> fieldMap = new HashMap<String, String>();
        for (Field field : fields) {
            fieldName = field.getName();
            if (field.getModifiers() == Modifier.PUBLIC) {
                try {
                    fieldValue = field.get(entity);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } else {
                fieldValue = invokeGet(entity, fieldName);
            }
            fieldMap.put(fieldName, fieldValue == null ? "" : fieldValue
                    .toString());
        }
        return fieldMap;
    }

    /**
     * 将实体类对象的属性值转换成属性名为key，属性值为value的Map<String,Object>并返回.
     * 其中实体类中有其他自定义对象类型的属性。
     * 
     * @param entity
     *            需要转换的实体类对象
     * @param packageName
     *            自定义对象类型属性的对象所在的包名
     * @return 转换后的Map<String,Object>
     */
    @SuppressWarnings("unchecked")
    public static Map<String, Object> beanToMap(Object entity,
            String packageName) {
        Class c = entity.getClass();
        Object fieldValue = null;
        String fieldName = null;
        Field[] fields = c.getDeclaredFields();
        Map<String, Object> fieldMap = new HashMap<String, Object>();
        for (Field field : fields) {
            fieldName = field.getName();
            if (field.getModifiers() == Modifier.PUBLIC) {
                try {
                    fieldValue = field.get(entity);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } else {
                fieldValue = invokeGet(entity, fieldName);
            }
            if (fieldValue != null
                    && fieldValue.getClass().getName().startsWith(packageName)) {
                fieldValue = beanToMap(fieldValue, packageName);
            }
            fieldMap.put(fieldName, fieldValue);
        }
        return fieldMap;
    }

    private static Object invokeGet(Object entity, String fieldName) {
        try {
            Method method = entity.getClass().getMethod(
                    "get" + StringUtil.firstToUpper(fieldName));
            return method.invoke(entity);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 将一个实体对象(已有部分属性赋值)转换成有值属性组成的条件查询SQL语句<br>
     * <font color="red">注意：需要转换的对象的属性若是基本类型则得用包装类代替</font>
     * 
     * @param entity
     *            需要转换的实体类对象
     * @return 转换后的条件查询SQL语句字符串
     */
    public static String beanToWhereSql(Object entity) {
        StringBuffer ret = new StringBuffer(" where 1=1");
        Map<String, Object> map = beanToMap(entity, "cn.org.jshuwei.j2ee.util");
        for (Map.Entry<String, Object> entry : map.entrySet()) {
            Object value = entry.getValue();
            String key = entry.getKey();
            if (value != null) {
                ret.append(" and ").append(key).append("=").append(value);
            }
        }
        return ret.toString();
    }
}