java Annotation 拼装SQL话语(转)

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;

@Target(ElementType.FIELD)??
@Retention(RetentionPolicy.RUNTIME)?
@interface FiledRef
{
??? String fieldName();
}

@Target(ElementType.TYPE)??
@Retention(RetentionPolicy.RUNTIME)
@interface TableRef
{
??? String tableName();
}

@TableRef(tableName = "MobDevice")
public class ReflectTest
{
??? @FiledRef(fieldName = "ID")
??? private Long id;

??? @FiledRef(fieldName = "DEVICE_NAME")
??? private String name;

??? @FiledRef(fieldName = "DEVICE_CODE")
??? private String code;

??? public ReflectTest(Long id, String name, String code)
??? {
??????? this.id = id;
??????? this.name = name;
??????? this.code = code;
??? }

??? 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 getCode()
??? {
??????? return code;
??? }

??? public void setCode(String code)
??? {
??????? this.code = code;
??? }

??? /**
???? * @description
???? * @author zhangml
???? * @date May 17, 2010 4:39:30 PM
???? * @param args
???? */
??? public static void main(String[] args)
??? {
??????? ReflectTest rt = new ReflectTest(new Long(1), "2", "3");
??????? StringBuffer sql = new StringBuffer("");
??????? buildSql(rt, sql);
??????? System.err.println(sql);
??? }

??? public static void buildSql(Object obj, StringBuffer sb)
??? {
??????? Class<? extends Object> clazz = obj.getClass();
??????? Field[] fields = clazz.getDeclaredFields();
??????? if (clazz.isAnnotationPresent(TableRef.class))
??????? {
??????????? TableRef tr = (TableRef) clazz.getAnnotation(TableRef.class);
??????????? sb.append("SELECT * FROM ");
??????????? sb.append(tr.tableName());
??????? }
??????? if (fields != null && fields.length > 0)
??????? {
??????????? sb.append(" WHERE ");
??????????? for (Field field : fields)
??????????? {
??????????????? try
??????????????? {
??????????????????? Object value = field.get(obj);
??????????????????? if (value != null && field.isAnnotationPresent(FiledRef.class))
??????????????????? {
??????????????????????? FiledRef fr = field.getAnnotation(FiledRef.class);
??????????????????????? sb.append(fr.fieldName() + "=" + value);
??????????????????????? sb.append(" AND ");
??????????????????? }
??????????????? }
??????????????? catch (Exception e)
??????????????? {
??????????????????? e.printStackTrace();
??????????????? }
??????????? }
??????????? int length = sb.length();
??????????? sb.delete(length-5, length);
??????? }
??? }

}

执行结果：SELECT * FROM MobDevice WHERE ID=1 AND DEVICE_NAME=2 AND DEVICE_CODE=3