java实现从实体到SQL语句的转换（二）

前面写过一篇生成insert语句的博客，今天把CRUD的都完善了一下，需要的上次写的获取实体信息的类，这里就不贴出来了【点击打开查看】

下面是完整的代码：

package tan.code.utils;

import java.util.List;
import java.util.Map;

/**
 * 简单的SQL语句拼装类 ;要求数据库表名及列命和实体保持一致;
 *
 * @author Mr_Tank_
 *
 * @param <T>
 */
public class SQLStringHelper<T> {

	private EntityHelper entityHelper = new EntityHelper();

	/**
	 * 根据传入的实体生成Insert SQL語句
	 *
	 * @param entity
	 * @return 拼接好的sql语句
	 */
	@SuppressWarnings("unchecked")
	public String createInsert(T entity) {
		String sql = "Insert into ";
		String column = ""; // 列
		String c_values = ""; // 列值
		List<Map<String, Object>> list = entityHelper.getFiledsInfo(entity);
		sql += list.get(0).get("obj_name").toString() + " ";
		for (int i = 0; i < list.size(); i++) {

			// 約定id在數據庫自動生成-20130807

			if (String.valueOf(list.get(i).get("f_name")).equals("id")) {
				i++;
			} else if (list.get(i).get("f_value") != null) {
				column += list.get(i).get("f_name") + ",";
				c_values += "'" + list.get(i).get("f_value") + "',";
			}

		}
		sql += "(" + column.substring(0, column.length() - 1) + ") values ("
				+ c_values.substring(0, c_values.length() - 1) + ");";

		return sql;

	}

	/**
	 * 拼裝Delete SQL語句
	 *
	 * @param entity
	 * @param id
	 *            实体id
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public String createDelete(T entity, int id) {
		String sql = "delete from ";
		List<Map<String, Object>> list = entityHelper.getFiledsInfo(entity);
		sql += list.get(0).get("obj_name").toString() + " where id=" + id + ";";
		return sql;
	}

	/**
	 * 查找
	 *
	 * @param entity
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public String createSelect(T entity) {
		String sql = "select * from ";
		String column = ""; // 列
		List<Map<String, Object>> list = entityHelper.getFiledsInfo(entity);
		sql += list.get(0).get("obj_name").toString() + " where ";
		for (int i = 0; i < list.size(); i++) {

			// 約定id在數據庫自動生成-20130807

			// id計數不能從0開始
			// 如果知道id直接根据id生成sql语句就可以了
			if (String.valueOf(list.get(i).get("f_name")).equals("id")
					&& !String.valueOf(list.get(i).get("f_value")).equals("0")) {
				sql += "id=" + list.get(i).get("f_value");
				return sql;
			} else if (list.get(i).get("f_value") != null) {

				column += list.get(i).get("f_name") + " like %"
						+ list.get(i).get("f_value") + "% or ";
			}
		}
		return sql += column.substring(0, column.length() - 4) + ";";

	}

	/**
	 * 根据id更新实体数据
	 *
	 * @param entity
	 * @param id
	 *            实体id
	 * @return 拼装好的 Update SQL语句
	 */
	@SuppressWarnings("unchecked")
	public String createUpdate(T entity, int id) {
		String sql = "update ";
		String column = ""; // 列
		List<Map<String, Object>> list = entityHelper.getFiledsInfo(entity);
		sql += list.get(0).get("obj_name").toString() + " set ";
		for (int i = 0; i < list.size(); i++) {

			// id不能修改
			if (String.valueOf(list.get(i).get("f_name")).equals("id")) {
				i++;
			} else if (list.get(i).get("f_value") != null) {
				column += list.get(i).get("f_name") + "='"
						+ list.get(i).get("f_value")+"',";
			}

		}
		return sql +=column.substring(0, column.length()-1) + " where id='" + id+"'";

	}
}

测试【其中可以使用任意实体类替代测试代码里面的的Tutor类】：

	@Test
	public void test() {
		// fail("Not yet implemented");
		Tutor tutor = new Tutor();
		tutor.setId(3);
		//tutor.setTitle("寻找一個初三物理長期家教");
		tutor.setProvince("广西壮族自治区");
		tutor.setCity("桂林");
		tutor.setRegion("朝阳区");
		//tutor.setPatriarch("王先生");
		tutor.setPhone("139772109981");
		tutor.setGrade("初三");
		tutor.setSubject("物理");
		tutor.setPay(50);

		SQLStringHelper<Tutor> sqlStringHelper = new SQLStringHelper<Tutor>();
		System.out.println(sqlStringHelper.createInsert(tutor));
		System.out.println(sqlStringHelper.createDelete(tutor, 1));
		System.out.println(sqlStringHelper.createSelect(tutor));
		System.out.println(sqlStringHelper.createUpdate(tutor, 2));
	}

测试结果：

Insert into Tutor (subject,grade,pay,phone,browse,province,city,region,wb_num) values ('物理','初三','50.0','139772109981','0','广西壮族自治区','桂林','朝阳区','0');
delete from Tutor where id=1;
select * from Tutor where id=3
update Tutor set subject='物理',grade='初三',pay='50.0',phone='139772109981',browse='0',province='广西壮族自治区',city='桂林',region='朝阳区',wb_num='0' where id='2'

以上只是本人的一些尝试，如有不足之处，请指出。