hibernate模拟实现insert

最新推荐文章于 2021-01-19 12:16:25 发布

袁崇焕

最新推荐文章于 2021-01-19 12:16:25 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/temp1989/article/details/39155689

该博客主要展示了如何使用Java代码模拟Hibernate的插入操作。通过创建Session类，定义了ORM映射，动态生成SQL语句，并利用反射调用对象方法获取属性值，最后执行PreparedStatement进行数据保存。示例中涉及了对学生对象（Student）的id、name和age属性的处理。

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package cn.test.main;

import java.lang.reflect.Method;
import java.sql.DriverManager;
import java.util.HashMap;
import java.util.Map;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;

public class Session {

	private String table;
	private String[] methods;
	private Map<String, String> orm;

	public Session() {
		table = "Student";
		// key is column, value is property
		orm = new HashMap<String, String>();
		orm.put("id", "id");
		orm.put("name", "name");
		orm.put("age", "age");
		methods = new String[orm.size()];
	}

	public String createSQL() {
		StringBuilder s1 = new StringBuilder();
		int index = 0;
		for (String column : orm.keySet()) {
			String property = orm.get(column);
			property = Character.toUpperCase(property.charAt(0))
					+ property.substring(1);
			// getId getName getAge
			methods[index++] = "get" + property;
			s1.append(column);
			s1.append(",");
		}
		s1.subSequence(0, s1.length() - 1);
		StringBuilder s2 = new StringBuilder();
		for (int i = 0; i < orm.size(); ++i) {
			s2.append("?,");
		}
		s2.append(s2.subSequence(0, s2.length() - 1));
		// insert into Student(id,name,age) values (?,?,?)
		String sql = "insert into " + table + "(" + s1 + ")" + " values (" + s2
				+ ")";
		return sql;
	}

	public void save(Student student) {
		String sql = createSQL();
		Connection conn = DriverManager.getConnection(
				"jdbc:mysql://localhost/hibernate", "root", "root");
		PreparedStatement statement = conn.prepareStatement(sql);
		for (int i = 0; i < methods.length; ++i) {
			Method method = student.getClass().getMethod(methods[i]);
			Class returnType = method.getReturnType();
			if (returnType.getName().equals("java.lang.String")) {
				String returnValue = (String) method.invoke(student);
				statement.setString(i + 1, returnValue);
			}
			if (returnType.getName().equals("int")) {
				Integer returnValue = (Integer) method.invoke(student);
				statement.setInt(i + 1, returnValue);
			}
		}
	}
}