反射3：利用java反射技术将查询结果封装成对象

布满荆棘的人生 2022-08-09 01:52 176阅读 0赞

package cn.itcast.domain;
    
    import java.lang.reflect.Method;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.ResultSetMetaData;
    
    import cn.itcast.jdbc.JdbcUtils;
    
    public class ORMTest { 
    
        public static void main(String[] args) throws Exception {
            User user = getUser("select id as Id , name as Name , birthday as Birthday , money as Money from user where id = 1");
            System.out.println(user);
        }
    
        // 将数据库中读出的数据放到新建的User对象中,返回User对象
        static User getUser(String sql) throws Exception {
            Connection conn = null;
            PreparedStatement ps = null;
            ResultSet rs = null;
    
            try {
                conn = JdbcUtils.getConnection();
                ps = conn.prepareStatement(sql);
                rs = ps.executeQuery();
                ResultSetMetaData rsmd = rs.getMetaData();
                int count = rsmd.getColumnCount();
                String[] colNames = new String[count];
                for (int i = 1; i <= count; i++) {
                    colNames[i - 1] = rsmd.getColumnName(i);
                }
    
                User user = null;
    
                while (rs.next()) {
                    user = new User();
                    Method[] ms = user.getClass().getMethods();
                    for (int i = 0; i < colNames.length; i++) {
                        String colName = colNames[i];
                        String methodName = "set" + colName; // set方法的名字
                        for (Method m : ms) {
                            if (methodName.equals(m.getName()))
                                m.invoke(user, rs.getObject(colName));
                        }
                    }
                }
                return user;
            } finally {
                JdbcUtils.free(rs, ps, conn);
            }
        }
    }