jdbc的基础插入方法

package org.tlgg.utils;


import java.lang.reflect.*;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;


import org.tlgg.model.Roles;
import org.tlgg.model.Users;


public class DBTools {
//创建一个静态全局变量conn
private static Connection conn;
//放在静态初始化块中，每次一加载类就把驱动加载到内存中
static{
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
//新建一个连接返回
private static Connection getConnection(){
try {
conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","system","123456");
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}

public static<T> int insertObject(T type){
int i=0;
List<String> columns = new ArrayList<String>();
//通过反射获取类，然后获取该类的所有属性，保存到columns中
Class clazz = type.getClass();
for(Field field : clazz.getDeclaredFields()){
//当属性的类型为字符串或者整型的时候，添加到columns中
if((field.getType().equals(String.class))||(field.getType().equals(int.class))){

columns.add(field.getName());
}
}
//最后一位个属性role为引用类型，需要移除掉
//columns.remove(columns.size()-1);
String sql = createInsertSql(clazz, columns);
System.out.println(sql);
try {
PreparedStatement preparedStatement = getConnection().prepareStatement(sql);
int index = 1;

for(String param:columns){
//getDeclaredMethods()和getMethods()的区别是：前者只会返回当前类中声明的方法，不会返回继承与其他类的方法
for(Method method :clazz.getDeclaredMethods()){
if(method.getName().equalsIgnoreCase("get"+param)){
//给sql语句中后面的？设值为type对象调用当前method的返回值
preparedStatement.setObject(index, method.invoke(type, null));
index++;
}
}
}
i = preparedStatement.executeUpdate();
} catch (SQLException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
e.printStackTrace();
}
return i;
}
/**
* 通过泛型T的包装类和String对象的参赛集合 生成插入的字符串返回
* @param Class<T> c,List<String> columns
* @return String 插入的sql语句
* */
private static<T> String createInsertSql(Class<T> c,List<String> columns){
StringBuffer buffer = new StringBuffer();
buffer.append("insert into ");
buffer.append(c.getSimpleName());
buffer.append("(");
//通过增强for循环取出columns中的要插入参数的列名
for(String param : columns){
buffer.append(param);
buffer.append(",");
}
//最后一个列名不需要,要)
buffer.delete(buffer.length()-1, buffer.length());
buffer.append(") ");
//目前语句为：insert into users (id,name,password,roleid)
buffer.append("values(");
for(String param : columns){
buffer.append("?");
buffer.append(",");
}
buffer.delete(buffer.length()-1, buffer.length());
buffer.append(")");
//目前语句为：insert into users (id,name,password,roleid) valuse(?,?,?,?)
return buffer.toString();
}

public static void main(String[] args){
List columns = new ArrayList();

Users user = new Users(12307,"友善哥","123",2,null);
System.out.println(insertObject(user));
//System.out.println(String.class);
//System.out.println(int.class);
/*Class clazz = Users.class;
for(Field field : clazz.getDeclaredFields()){
columns.add(field.getName());
System.out.println(field.getName());
}
columns.remove(columns.size()-1);
for (Object object : columns) {
System.out.println(object);
}
System.out.println(createInsertSql(clazz, columns));
//System.out.println();
for(Method method :clazz.getDeclaredMethods()){
System.out.println(method.getName());
}*/
}
}