小白都在变强！Oracle反射插入与查询sql练习
1.jdbc的封装
package util;
import java.sql.*;
public class JDBCUtil {
public static final String URL = "jdbc:oracle:thin:@localhost:1521:orcl";
public static final String USERNAME = "scott";
public static final String PASSWORD = "tiger";
//初始化连接
static{
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/*
*
* @Description
* @Date 18:45 2019/11/12
* @Param
* @return
* 获得connection
**/
public static Connection getConnection() {
try {
return DriverManager.getConnection(URL,USERNAME,PASSWORD);
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
/*
* @Author chengpunan
* @Description
* @Date 18:47 2019/11/12
* @Param [connection, statement]
* @return void
* 关闭连接 connection和statement
**/
public static void closeConnection(Connection connection, Statement statement){
if(statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(connection != null){
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/*
* @Author chengpunan
* @Description
* @Date 18:47 2019/11/12
* @Param
* @return
* 关闭连接 connection和statement和resultSet
**/
public static void closeConnection(Connection connection, Statement statement, ResultSet resultSet){
if(resultSet != null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(connection != null){
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
2.需求：要查询N张表的数据，但是不想写N多的方法，能否写一个方法完成所有表的查询工作。
反射通用查询，中间插入了许多输出代码，方便了解值的类型
//获得set方法名
public String getSetName(String name){
return "set"+name.substring(0,1).toUpperCase()+name.substring(1);
}
/*
*sql SQL语句
*params 设置的参数
*clazz 某个表，也就是对象
*/
@Override
public List getRows(String sql, Object[] params, Class clazz) {
List list = new ArrayList();
Connection connection = null;
PreparedStatement pstem = null;
ResultSet resultSet =null;
try {
connection=JDBCUtil.getConnection();
pstem = connection.prepareStatement(sql);
//设置参数 pstem
if(params != null){
for (int i = 0; i <params.length ; i++) {
pstem.setObject(i+1,params[i]);
}
}
resultSet = pstem.executeQuery();
//返回元数据
ResultSetMetaData metaData = resultSet.getMetaData();
//查询每一行中包含多少列
int count = metaData.getColumnCount();
while (resultSet.next()){
//创建对象
Object obj = clazz.newInstance();
for (int i = 0; i <count ; i++) {
//从集合中获取但一列的值
Object objValue = resultSet.getObject(i + 1);
// System.out.println("objValus是："+objValue);
//获取列名
String columnName = metaData.getColumnName(i + 1).toLowerCase();
// System.out.println("columnName是："+columnName);
//获取属性名字
Field declaredField = clazz.getDeclaredField(columnName);
// System.out.println("declaredField是："+declaredField);
//获得类中的 set方法，调用了上面的获取set的方法
Method method = clazz.getMethod(getSetName(columnName), declaredField.getType());
if(objValue instanceof Number){
//转成Number是应为java的数值不能直接用在Oracle中
Number number = (Number) objValue;
// System.out.println("number------>"+number);
String fname = declaredField.getType().getName();
// System.out.println("fname------>"+fname);
if("int".equals(fname) || "java.lang.Integer".equals(fname)){
method.invoke(obj,number.intValue());
}else if("byte".equals(fname)||"java.lang.Byte".equals(fname)){
method.invoke(obj,number.byteValue());
}else if("short".equals(fname)||"java.lang.Short".equals(fname)){
method.invoke(obj,number.shortValue());
}else if("long".equals(fname)||"java.lang.Long".equals(fname)){
method.invoke(obj,number.longValue());
}else if("float".equals(fname) || "java.lang.Float".equals(fname)){
method.invoke(obj,number.floatValue());
}else if("double".equals(fname)||"java.lang.Double".equals(fname)){
method.invoke(obj,number.doubleValue());
}
}else {
method.invoke(obj,objValue);
}
}
list.add(obj);
}
// System.out.println(count);
} catch (Exception e) {
e.printStackTrace();
}finally {
JDBCUtil.closeConnection(connection,pstem,resultSet);
}
return list;
}
3.需求：输入一个对象 我就能插入对应表中。
利用反射做出通用 sql插入
//获得get方法名
public String getGetName(String name){
return "get"+name.substring(0,1).toUpperCase()+name.substring(1);
}
/*
*object 插入的表，也就是对象
*/
@Override
public void save(Object object) {
//存储有值的属性
List<String> list = new ArrayList<>();
//存储属性值
List<Object> rList = new ArrayList<>();
Class<?> aClass = object.getClass();
Connection connection = null;
PreparedStatement pstem = null;
//获得表名
String name = aClass.getSimpleName().toUpperCase();
//获得所有属性
Field[] fields = aClass.getDeclaredFields();
Method method =null;
try {
for(Field field : fields){
//获得get方法
method = aClass.getMethod(getGetName(field.getName()));
//获取被设置值的属性
Object o = method.invoke(object);
//拿取属性和属性值
if(o != null) {
list.add(field.getName());
rList.add(o);
}
}
//拼接表字段和 ？
String str ="";
String resule ="";
for (String l :list){
resule += l+",";
str +="?,";
}
//切掉多余的 ,
str=str.substring(0,str.length()-1);
resule=resule.substring(0,resule.length()-1);
//拼接的sql
String sql ="insert into "+name+"("+resule+") values (" +str +")";
//获得连接
connection = JDBCUtil.getConnection();
pstem = connection.prepareStatement(sql);
//用拿取到的值设置回去
for (int i = 0; i <list.size() ; i++) {
pstem.setObject(i+1,rList.get(i));
}
pstem.executeUpdate();
} catch (Exception e) {
e.printStackTrace();
}finally {
JDBCUtil.closeConnection(connection,pstem);
}
}