Hibernate的save方法的简单实现

目标：简单实现hibernate的save()方法。

1.首先我们假设我们从xml文件中已经获得了jdbc的连接，和属性和字段的映射表存入Map<String,String>中

2.创建一个实体类，和表Teacher（两者对应）

public class Teacher {
    private int id;
    private int height;
    private String name;
    

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
    public int getHeight() {
        return height;
    }
    public void setHeight(int height) {
        this.height = height;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    

}

3.创建一个Session类，里面包含save方法

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

public class Session {

    Map<String,String> map;
    String TableName = "teacher";
    String[] MethodNames;
    
    //假设我们已经从配置文件中拿到了id name height映射关系
    public Session() {
        map = new HashMap<String,String>();
        map.put("id", "id");
        map.put("name", "name");
        map.put("height", "height");
        
        MethodNames = new String[map.size()];
        
    }
    
//    public String[] getMethods(Teacher t) throws NoSuchMethodException, SecurityException{
//        //getAge
//        for(int i = 0;i<MethodNames.length;i++){
//            String str = map.get(key)
//            str = Character.toUpperCase(str.charAt(0)) + str.substring(1);
//            MethodNames[i] = "get"+str;
//            System.out.println(MethodNames[i]);
//        }
//        return MethodNames;
//    }
    
    public void save(Teacher t) throws Exception{
        
        t.getClass().forName("com.mysql.jdbc.Driver");
        Connection con =  DriverManager.getConnection("jdbc:mysql://localhost/text02","root","6530033197");
        String sql = creatSql();
        PreparedStatement ps = con.prepareStatement(sql);
        
        
        /*ps.setInt(1,t.getId());
        ps.setString(2,t.getName());
        ps.setInt(3, t.getHeight()); */
        Class c = t.getClass();
        
        for(int i = 0;i<map.size();i++){
            Method m = c.getMethod(MethodNames[i]);
            Class c1 = m.getReturnType();
            System.out.println(c1.getName());
            if(c1.getName().equals("java.lang.String")){
                ps.setString(i+1, (String) m.invoke(t));
            }
            if(c1.getName().equals("int")){
                ps.setInt(i+1,(int)m.invoke(t));
            }
        }
        
        ps.executeUpdate();
        ps.close();
        con.close();
        
    }
    
    public String creatSql(){
        String sql = "";
        String str1 = "";
        String str2 = "";
        
        int index = 0;
        for(String str:map.keySet()){
            String str3 = map.get(str);
            str3 = Character.toUpperCase(str.charAt(0)) + str.substring(1);
            MethodNames[index] = "get"+str3;
            
            //System.out.println(MethodNames[index]);
            
            str1 +=str+",";
            index++;
        }
        str1 = str1.substring(0, str1.length()-1);
        //System.out.println(str1);
        
        for(int x = 0;x<map.size();x++){
            str2 += "?,";
        }
        
        str2 = str2.substring(0, str2.length()-1);
        //System.out.println(str2);
        
        
        //insert into teacher("id","name","height")values(?,?,?);
        sql = "insert into "+TableName+"("+str1+") values("+str2+")";
        System.out.println(sql);
        return sql;
    }

}

4.用一个类做测试：

public class TeacherText {

    public static void main(String[] args) throws Exception {
        Teacher t = new Teacher();
        t.setId(2);
        t.setHeight(180);
        t.setName("张大平");
        
        Session s = new Session();
        s.save(t);
    }

}

完成，一个简单的save()方法就完成了，因为只是最简单的封装，所以代码很乱。