简仿Mybatis实现原理的小工具

直接上实现代码： 

package com.wzc.daohelper;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.sql.*;
import java.util.*;

/**
 * @author WANGZIC
 */
public class WZCDaoHelper {

    private static final String START_PARAM ="#{";

    private static final String END_PARAM ="}";

    private static final String SELECT="SELECT";

    private static final String XML_TYPE=".xml";

    private String driverName = null;

    private String url = null;

    private String username = null;

    private String password= null;

    private String scanPath= null;

    private Map<String,String> sqlCollection =new HashMap<String,String>();

    public WZCDaoHelper() {
        try {
            Properties properties = new Properties();
            File configFile =new File(WZCDaoHelper.class.getResource("com/wzc/daohelper/config.properties").getPath().substring(1));
            if(!configFile.exists()){
                throw new RuntimeException("未找到配置文件");
            }
            InputStream is = new FileInputStream(configFile);
            properties.load(is);
            //读取属性
            this.driverName = properties.getProperty("jdbc.driverName");
            this.url = properties.getProperty("jdbc.url");
            this.username = properties.getProperty("jdbc.username");
            this.password = properties.getProperty("jdbc.password");
            this.scanPath =this.getClass().getResource("/").getPath()+properties.getProperty("dao.scanPath");
            scanDaoXML(scanPath);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public WZCDaoHelper(String configFilePath) {
        try {
            Properties properties = new Properties();
            File configFile =new File(configFilePath);
            if(!configFile.exists()){
                throw new RuntimeException("未找到配置文件");
            }
            InputStream is = new FileInputStream(configFile);
            properties.load(is);
            //读取属性
            this.driverName = properties.getProperty("jdbc.driverName");
            this.url = properties.getProperty("jdbc.url");
            this.username = properties.getProperty("jdbc.username");
            this.password = properties.getProperty("jdbc.password");
            this.scanPath = this.getClass().getResource("/").getPath()+properties.getProperty("dao.scanPath");
            scanDaoXML(scanPath);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void scanDaoXML(String path){
        Map<String,String> sqlmap =new HashMap<String,String>();
        File dir = new File(path);
        if(dir.exists()){
            File[] files = dir.listFiles();
            if(files!=null){
                for(File f:files){
                    if(f.isDirectory()){
                        scanDaoXML(f.getPath());
                    }else{
                        if(f.getName().endsWith(XML_TYPE)){
                            try {
                                DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
                                DocumentBuilder dbd = dbf.newDocumentBuilder();
                                Document doc = dbd.parse(f);
                                Element root = doc.getDocumentElement();
                                String namespace = root.getAttribute("namespace");
                                NodeList children =root.getElementsByTagName("sql");
                                for(int i=0;i<children.getLength();i++){
                                    Element element= (Element) children.item(i);
                                    sqlmap.put(namespace+"."+element.getAttribute("id"),element.getTextContent().trim());
                                }
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
        }
        this.sqlCollection= sqlmap;
    }

    public List<Map<String,Object>> executeSQL(String sqlId, Map<String,Object> params){
        String sql =sqlCollection.get(sqlId);
        if(sql==null){
            throw new RuntimeException("未找到id为："+sqlId+"的sql语句");
        }
        List<Map<String,Object>> resultList =new ArrayList<>();
        ResultSet rs = null;
        PreparedStatement ps=null;
        Statement st =null;
        Connection conn  = getConn();
        if(conn==null){
            throw  new RuntimeException("未获取到数据库连接，请检查配置信息");
        }
        try {
            if(sql.contains(START_PARAM)){
                StringBuilder builder = new StringBuilder();
                List<Object> paramValList =new ArrayList<>();
                while (sql.contains(START_PARAM)){
                    int startIndex = sql.indexOf(START_PARAM);
                    int endIndex = sql.indexOf(END_PARAM);
                    String paramKey =sql.substring(startIndex+2,endIndex);
                    if(params.containsKey(paramKey)){
                        paramValList.add(params.get(paramKey));
                    }else{
                        throw new RuntimeException("缺少"+paramKey+"字段的值");
                    }
                    sql =builder.append(sql.substring(0,startIndex)).append(" ? ").append(sql.substring(endIndex+1,sql.length())).toString();
                    builder.delete(0,builder.length());
                }
                ps= conn.prepareStatement(sql);
                int num =1;
                for(Object paramVal:paramValList){
                    if(paramVal instanceof java.lang.String){
                        ps.setString(num, (String) paramVal);
                    }else if(paramVal instanceof java.lang.Integer){
                        ps.setInt(num, (Integer)  paramVal);
                    }else{
                        ps.setObject(num,paramVal);
                    }
                    num++;
                }
                if(sql.toUpperCase().startsWith(SELECT)){
                    rs =ps.executeQuery();
                    resultList =parseResultSetToListMap(rs);
                }else{
                    int res = ps.executeUpdate();
                    Map<String,Object> resmap =new HashMap<String,Object>();
                    resmap.put("update",res);
                    resultList.add(resmap);
                }
            }else{
                st= conn.createStatement();
                if(sql.toUpperCase().startsWith(SELECT)){
                    rs =st.executeQuery(sql);
                    resultList =parseResultSetToListMap(rs);
                }else{
                    int res = st.executeUpdate(sql);
                    Map<String,Object> resmap =new HashMap<String,Object>();
                    resmap.put("update",res);
                    resultList.add(resmap);
                }

            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            close(conn,st,ps,rs);
        }
        return resultList;

    }

    /**
     * 将查询结果转换为List<Map<String,Object>>类型
     * @param rs
     * @return List<Map<String,Object>>
     */
    private static List<Map<String,Object>> parseResultSetToListMap(ResultSet rs) {
        List<Map<String,Object>> results=new ArrayList<Map<String,Object>>();
        try {
            if(rs==null){
                return results;
            }
            ResultSetMetaData rsmd = rs.getMetaData();
            int colLen=rsmd.getColumnCount();
            while(rs.next()){
                Map<String,Object> map = new HashMap<String,Object>();
                for(int i = 0;i < colLen;i++){
                    String colName = rsmd.getColumnName(i+1);
                    map.put(colName,rs.getObject(colName));
                }
                results.add(map);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return results;
    }

    /**
     * 将查询结果转换为指定类型的对象
     * @param rs
     * @param cls
     * @param <T>
     * @return
     */
    private static <T> List<T> parseResultSetToBean(ResultSet rs,Class<T> cls) {
        try {
            List<T> list=new ArrayList<T>();
            //将查询的所有数据转换为对象添加到集合
            while(rs.next()){
                //实例化对象
                T obj=cls.newInstance();
                //获取类中所有的属性
                Field[] arrf=cls.getDeclaredFields();
                //遍历属性
                for(Field f:arrf){
                    //设置忽略访问校验
                    f.setAccessible(true);
                    //为属性设置内容
                    f.set(obj, rs.getObject(f.getName()));
                }
                //添加到集合
                list.add(obj);
            }
            return list;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    private Connection getConn(){
        Connection conn = null;
        try {
            Class.forName(this.driverName);
            //2. 建立连接 参数一： 协议 + 访问的数据库 ， 参数二： 用户名 ， 参数三： 密码。
            conn = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }
    private static void close(Connection conn,Statement st,PreparedStatement ps,ResultSet rs){
        closeConn(conn);
        closePs(ps);
        closeSt(st);
        closeRs(rs);
    }
    private static void closeRs(ResultSet rs){
        try {
            if(rs != null){
                rs.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            rs = null;
        }
    }
    private static void closeSt(Statement st){
        try {
            if(st != null){
                st.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            st = null;
        }
    }
    private static void closePs(PreparedStatement ps){
        try {
            if(ps != null){
                ps.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            ps = null;
        }
    }
    private static void closeConn(Connection conn){
        try {
            if(conn != null){
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            conn = null;
        }
    }

    public static void main(String[] args) {
        System.out.println("欢迎使用WZCDaoHelper");
    }
}

 配置文件：

jdbc.driverName=com.mysql.jdbc.Driver
jdbc.username=root
jdbc.password=root
jdbc.url=jdbc:mysql://127.0.0.1:3306/mytest
dao.scanPath=

 

目录结构 

SQL.xml结构：

<?xml version="1.0" encoding="utf-8"?>
<DaoSQL namespace="user">
    <sql id="insertUser">
        insert into tb_user (id,username,password,birthdate,signature) values(#{id},#{username},#{password},#{birthdate},#{signature})
    </sql>
    <sql id="updatePassword">
        update tb_user set password=#{password} where id=#{id}
    </sql>
    <sql id="deleteById">
        DELETE FROM tb_user WHERE id=#{id}
    </sql>
    <sql id="selectAll">
        select * from tb_user
    </sql>
    <sql id="selectById">
        select * from tb_user where id=#{id}
    </sql>
</DaoSQL>