利用Annotation构建针对POJO进行增删改操作

package com.core.annotation;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**   
 * @author zy 
 * @version 创建时间：Jul 2, 2010 2:39:20 PM  
 */
@Target({TYPE})
@Retention(RUNTIME)
public @interface Table {

	public abstract String name() default "";

	public abstract String catalog() default "";

	public abstract String schema()  default "";

}


package com.core.annotation;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**   
 * @author zy 
 * @version 创建时间：Jul 2, 2010 2:54:28 PM  
 */
@Target({FIELD,METHOD})
@Retention(RUNTIME)
public @interface Column {

	public abstract String name() default "";

	public abstract boolean unique() default false;

	public abstract boolean nullable() default true;

	public abstract String type() default "string";

	public abstract String definition() default "";

	public abstract int length() default 32;	

}


package com.entity;

import java.io.Serializable;

import com.core.annotation.Column;
import com.core.annotation.Table;

/**   
 * @author zy 
 * @version 创建时间：Jul 6, 2010 9:15:18 AM  
 */
@Table(name="T_USER")
public class User implements Serializable{	

	private static final long serialVersionUID = 6602217772155966261L;

	String id;
	String name;
	String sex;

	@Column(name="USER_NAME")
	public String getName() {
		return name;
	}

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

	@Column(name="SEX")
	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
}


package com.core.util;

import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import com.entity.User;
import com.core.annotation.Column;
import com.core.annotation.Table;

/**   
 * @author zy 
 * @version 创建时间：Jul 2, 2010 2:00:55 PM  
 */
public class AnnotationUtil {

	@SuppressWarnings("unchecked")
	public static String save(User u){		
		String temp = null;		
		StringBuffer sb = new StringBuffer();
		String id = String.valueOf(u.getId());
		if(id == null || id.trim().equals("")){	
			StringBuffer key = new StringBuffer();
			StringBuffer value = new StringBuffer();
			sb.append("insert into ");
			Class c = u.getClass();
			Object [] obj = null;
			if(c != null && c.isAnnotationPresent(Table.class)){		
				Table table = (Table) c.getAnnotation(Table.class);
				try {
					temp = table.name();
					if(temp.trim().equals("")){
						sb.append(c.getName().trim());
					}else{
						sb.append(temp.trim());
					}
				} catch (Exception e) {
					sb.append(c.getName().trim());
				}			
			}else{
				sb.append(c.getName().trim());
			}

			Method [] method = u.getClass().getDeclaredMethods();
			for(Method m : method){
				if(m != null && m.isAnnotationPresent(Column.class)){
					Column column = m.getAnnotation(Column.class);
					temp = column.name();
					if(temp.trim().equals("")){
						key.append(m.getName().substring(3).trim()).append(",");
					}else{
						key.append(temp.trim()).append(",");
					}	
					try {
						temp = String.valueOf(m.invoke(u, obj));
						value.append("'").append(temp.trim()).append("',");
					} catch (IllegalArgumentException e) {					
						e.printStackTrace();
						value.append("'',");
					} catch (IllegalAccessException e) {					
						e.printStackTrace();
						value.append("'',");
					} catch (InvocationTargetException e) {					
						e.printStackTrace();
						value.append("'',");
					}
				}
			}		
			key.deleteCharAt(key.lastIndexOf(","));
			value.deleteCharAt(value.lastIndexOf(","));
			sb.append(" (").append(key).append(") values");
			sb.append(" (").append(value).append(")");
		}else{
			sb.append("update ");
			Class c = u.getClass();
			Object [] obj = null;
			if(c != null && c.isAnnotationPresent(Table.class)){		
				Table table = (Table) c.getAnnotation(Table.class);
				try {
					temp = table.name();
					if(temp.trim().equals("")){
						sb.append(c.getName().trim());
					}else{
						sb.append(temp.trim());
					}
				} catch (Exception e) {
					sb.append(c.getName().trim());
				}			
			}else{
				sb.append(c.getName().trim());
			}
			sb.append(" set ");
			Method [] method = u.getClass().getDeclaredMethods();
			for(Method m : method){
				if(m != null && m.isAnnotationPresent(Column.class)){
					Column column = m.getAnnotation(Column.class);
					temp = column.name();
					if(temp.trim().equals("")){
						sb.append(m.getName().substring(3).trim()).append("=");
						try {
							temp = String.valueOf(m.invoke(u, obj));
							sb.append("'").append(temp.trim()).append("',");
						} catch (IllegalArgumentException e) {					
							e.printStackTrace();
							sb.append("'',");
						} catch (IllegalAccessException e) {					
							e.printStackTrace();
							sb.append("'',");
						} catch (InvocationTargetException e) {					
							e.printStackTrace();
							sb.append("'',");
						}
					}else{						
						sb.append(temp.trim()).append("=");
						try {
							temp = String.valueOf(m.invoke(u, obj));
							sb.append("'").append(temp.trim()).append("',");
						} catch (IllegalArgumentException e) {					
							e.printStackTrace();
							sb.append("'',");
						} catch (IllegalAccessException e) {					
							e.printStackTrace();
							sb.append("'',");
						} catch (InvocationTargetException e) {					
							e.printStackTrace();
							sb.append("'',");
						}
					}	

				}
			}		
			sb.deleteCharAt(sb.lastIndexOf(","));			
			sb.append(" where id='").append(id.trim()).append("'");
		}
		return sb.toString();
	}


	@SuppressWarnings("unchecked")
	public static String delete(User u,Serializable id){		
		String temp = null;		
		StringBuffer sb = new StringBuffer("delete from ");
		Class c = u.getClass();	
		if(c != null && c.isAnnotationPresent(Table.class)){		
			Table table = (Table)c.getAnnotation(Table.class);
			try {
				temp = table.name();
				if(temp.trim().equals("")){
					sb.append(c.getName().trim());
				}else{
					sb.append(temp.trim());
				}
			} catch (Exception e) {
				sb.append(c.getName().trim());
			}			
		}else{
			sb.append(c.getName().trim());
		}
		sb.append(" where id='").append(String.valueOf(id)).append("'");
		return sb.toString();
	}

	@SuppressWarnings("unchecked")
	public static void main(String[] args) {
		User user = new User();	
		user.setId("234");
		user.setName("历史");
		user.setSex("男");
		System.out.println(save(user));		
		System.out.println(delete(user,"123"));
	}
}