java反射应用

package cn.sxt.TestClass;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import cn.sxt.model.Dept;
import cn.sxt.util.DBUtil;

public class TestUser {
    public static void main(String[] args) {
        String sql = "select * from dept";

        List list = TestUser.rows2beans(sql, Dept.class);
        for (Object d : list) {
            // Dept dept = (Dept)d;
            System.out.println(d);

        }
    }

    public static List rows2beans(String sql, Class cls) {
        List list = new ArrayList<>();
        // 连接数据库
        Connection conn = DBUtil.getConnection();
        PreparedStatement ps = null;
        ResultSet rs = null;

        try {
            // 向数据库发送sql语句
            ps = conn.prepareStatement(sql);
            // 执行sql语句返回结果集
            rs = ps.executeQuery();
            // ResultSetMetaData可用于获取关于 ResultSet 对象中列的类型和属性信息的对象。
            ResultSetMetaData metaData = rs.getMetaData();
            // 获取查询的列数
            int count = metaData.getColumnCount();
            while (rs.next()) {
                // 创建反射实例
                Object obj = cls.newInstance();
                for (int i = 0; i < count; i++) {
                    // 获取数据库列名
                    String fileName = metaData.getColumnName(i + 1).toLowerCase();

                    // 通过列名获取类中的属性的描述
                    Field field = cls.getDeclaredField(fileName);

                    // 根据set方法名获取set方法对应的描述类
                    Method m = cls.getDeclaredMethod(getSetMethodName(fileName), field.getType());

                    // 判断接收的数据类型
                    Object object = rs.getObject(fileName);
                    if (object != null) {
                        if (field.getType().getName().equals("int")
                                || field.getType().getName().equals("Object.lang.Integer")) {
                            m.invoke(obj, rs.getInt(fileName));
                        } else if (field.getType().getName().equals("long")
                                || field.getType().getName().equals("Object.lang.Long")) {
                            m.invoke(obj, rs.getLong(fileName));
                        } else if (field.getType().getName().equals("short")
                                || field.getType().getName().equals("Object.lang.Short")) {
                            m.invoke(obj, rs.getShort(fileName));
                        } else if (field.getType().getName().equals("double")
                                || field.getType().getName().equals("Object.lang.Double")) {
                            m.invoke(obj, rs.getDouble(fileName));
                        } else if (field.getType().getName().equals("float")
                                || field.getType().getName().equals("Object.lang.Float")) {
                            m.invoke(obj, rs.getFloat(fileName));
                        } else if (field.getType().getName().equals("byte")
                                || field.getType().getName().equals("Object.lang.Byte")) {
                            m.invoke(obj, rs.getByte(fileName));
                        } else {
                            m.invoke(obj, object);
                        }

                    }
                }
                list.add(obj);

            }

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InstantiationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, ps, rs);
        }
        return list;
    }

    public static String getSetMethodName(String fileName) {

        return "set" + fileName.substring(0, 1).toUpperCase() + fileName.substring(1);
    }
}

package cn.sxt.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class DBUtil {
    private static String driver = "";
    private static String url = "";
    private static String user = "";
    private static String password = "";

    static {
        InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream("db.propertise");
        Properties pt = new Properties();
        try {
            pt.load(in);
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        driver = pt.getProperty("driver");
        url = pt.getProperty("url");
        user = pt.getProperty("user");
        password = pt.getProperty("password");

        try {
            Class.forName(driver);
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    /*
     * public static void main(String[] args) { System.out.println(driver);
     * System.out.println(url); System.out.println(user);
     * System.out.println(password);
     * 
     * }
     */
    //获取数据库连接
    public static Connection getConnection() {
        Connection conn = null;
        try {
            conn = DriverManager.getConnection(url, user, password);

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }
    
    public static void close(Connection conn, Statement ps) {
        if (ps != null) {
            try {

                ps.close();

            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }

    public static void close(Connection conn, Statement ps, ResultSet rs) {
        if (rs != null) {
            try {
                rs.close();

            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if (ps != null) {
            try {

                ps.close();

            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }
    
}