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Teemitze's questions

Martin Hope
Teemitze
Asked: 2022-04-10 15:16:24 +0000 UTC
  • 6

这是工作代码。我知道比较equals更好，但是为什么在创建具有相同值的新Double时，它指的是内存中的不同位置，而Long却没有。

public class Main {
    public static void main(String[] args) {
        Long firstLong = 1L;
        Long secondLong = 1L;

        Double firstDouble = 1.0;
        Double secondDouble = 1.0;


        System.out.println(firstLong == secondLong);
        System.out.println(firstDouble == secondDouble);
    }
}
java
Martin Hope
Teemitze
Asked: 2020-05-22 18:11:41 +0000 UTC
  • 0

如何获得默认值（28）？这是 github 上更完整的代码https://github.com/Teemitze/test

    package ru.otus.spring01.dao;

    import ru.otus.spring01.domain.Person;

    public class PersonDaoSimple implements PersonDao {

        public Person findByName(String name) {
            return new Person(name, 18);
        }

        public void setDefaultAge(String defaultAge) {
        }
    }

春天.xml


        <?xml version="1.0" encoding="UTF-8"?>
        <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
               xmlns="http://www.springframework.org/schema/beans"
               xsi:schemaLocation="http://www.springframework.org/schema/beans
                http://www.springframework.org/schema/beans/spring-beans.xsd">


            <bean id="personDao" class="ru.otus.spring01.dao.PersonDaoSimple">
                <property name="defaultAge" value="28"/>
            </bean>

            <bean id="personService" class="ru.otus.spring01.service.PersonServiceImpl">
                <constructor-arg name="dao" ref="personDao"/>
            </bean>

    </beans>
java
Martin Hope
Teemitze
Asked: 2020-05-03 17:06:18 +0000 UTC
  • 0
    post("/authentication", (req, res) -> {
        Authentication authentication = new Authentication();
        if (authentication.validate(req.headers("login"), req.headers("password"))) { // Проверяем логин и пароль
            UserService userService = new UserService();
            int id = userService.findByLogin(req.headers("login")).getId(); // Получаем id пользователя
            res.header("id", String.valueOf(id)); // Передаём в header id
            res.redirect("/myAnimals"); // Делаем редирект на страницу "/myAnimals"
        }
        return "NO";
    });

        get("/myAnimals", (req, res) -> {
        int id = Integer.parseInt(req.headers("id")); // Пытаемся получить переданный id с запроса post "/authentication" 
        return animalService.userAnimalsJson(id); // Возвращаем всех животных пользователя
    });

问题是我收到 500 错误。如果我也这样做，但我通过 cookie 传递 id，那么一切都很好。

日志中没有任何内容：

мая 03, 2019 12:51:56 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {4.0.4.Final}
мая 03, 2019 12:51:56 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.3.2.Final}
мая 03, 2019 12:51:56 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
мая 03, 2019 12:51:56 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
мая 03, 2019 12:51:56 PM org.hibernate.cfg.Configuration configure
INFO: HHH000043: Configuring from resource: hibernate.cfg.xml
мая 03, 2019 12:51:56 PM org.hibernate.cfg.Configuration getConfigurationInputStream
INFO: HHH000040: Configuration resource: hibernate.cfg.xml
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.dom4j.io.SAXContentHandler (file:/home/teemitze/.m2/repository/dom4j/dom4j/1.6.1/dom4j-1.6.1.jar) to method com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser$LocatorProxy.getEncoding()
WARNING: Please consider reporting this to the maintainers of org.dom4j.io.SAXContentHandler
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
мая 03, 2019 12:51:56 PM org.hibernate.cfg.Configuration doConfigure
INFO: HHH000041: Configured SessionFactory: null
Hibernate Configuration loaded
Hibernate serviceRegistry created
мая 03, 2019 12:51:56 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH000402: Using Hibernate built-in connection pool (not for production use!)
мая 03, 2019 12:51:56 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000401: using driver [org.postgresql.Driver] at URL [jdbc:postgresql://localhost:5432/soaweb]
мая 03, 2019 12:51:56 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000046: Connection properties: {password=****, user=root}
мая 03, 2019 12:51:56 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH000006: Autocommit mode: false
мая 03, 2019 12:51:56 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
мая 03, 2019 12:51:56 PM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.PostgreSQL9Dialect
мая 03, 2019 12:51:56 PM org.hibernate.engine.jdbc.internal.LobCreatorBuilder useContextualLobCreation
INFO: HHH000424: Disabling contextual LOB creation as createClob() method threw error : java.lang.reflect.InvocationTargetException
мая 03, 2019 12:51:56 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService
INFO: HHH000399: Using default transaction strategy (direct JDBC transactions)
мая 03, 2019 12:51:56 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory <init>
INFO: HHH000397: Using ASTQueryTranslatorFactory
Hibernate: select this_.id as id1_1_0_, this_.login as login2_1_0_, this_.password as password3_1_0_ from users this_ where this_.login like ?
Hibernate: select this_.id as id1_1_0_, this_.login as login2_1_0_, this_.password as password3_1_0_ from users this_ where this_.login like ?

页面出现以下错误

<html>
<body>
    <h2>500 Internal Server Error</h2>
</body>

java
Martin Hope
Teemitze
Asked: 2020-12-12 14:54:06 +0000 UTC
  • 10

您能否使用简单的 JAVA 代码示例来解释 DTO 是什么？为什么需要这个？

这段代码会是 DTO 吗？有两个类客户和银行

顾客

    import java.sql.Date;

class Customer {
    private String first_name;
    private String last_name;
    private String gedner;
    private Date age;
    private String address;


    Customer(String first_name, String last_name, String gedner, Date age, String address) {
        this.first_name = first_name;
        this.last_name = last_name;
        this.gedner = gedner;
        this.age = age;
        this.address = address;
    }

    public String getLast_name() {
        return last_name;
    }

    public String getFirst_name() {
        return first_name;
    }

    public String getGedner() {
        return gedner;
    }

    public Date getAge() {
        return age;
    }

    public String getAddress() {
        return address;
    }
}

银行

import java.sql.*;
import java.util.Scanner;


public class Bank {
    private static final String URL = "jdbc:mysql://localhost/bank?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
    private static final String USER = "root";
    private static final String PASSWORD = "root";

    Connection connection = null;
    PreparedStatement preparedStatement = null;
    Scanner in = new Scanner(System.in);

    public void connect() {
        try {
            connection = DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    Customer readCustomer() {
        Customer customer = null;
        try {
            preparedStatement = connection.prepareStatement("SELECT * FROM customers WHERE id_customer = ?");
            System.out.print("Введите id пользователя: ");
            preparedStatement.setInt(1, Integer.parseInt(in.next()));
            preparedStatement.execute();
            ResultSet rs = preparedStatement.executeQuery();
            String first_name = rs.getString("first_name");
            String last_name = rs.getString("last_name");
            String gender = rs.getString("gender");
            Date age = rs.getDate("age");
            String address = rs.getString("address");
            customer = new Customer(first_name, last_name, gender, age, address);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                preparedStatement.close();
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return customer;
    }
}

在 read 方法中，我将 ResultSet 变成了一个客户对象。这是DTO吗？

java