java - 为什么 SQL 查询不能直接使用类的实例

Question

我有一个程序，基本上应该将数据上传到本地主机数据库，XAMPP。该代码正在工作，除了一件事之外，它不插入指定的数据。它不会读取传入的值，因此会在数据库中用 0 填充它们。这就是令我困惑的地方。我已经从类的实例中很好地选择了变量，但它没有读取它们。为什么？变量不是私有(private)的。我尝试在数据库类上创建该类的实例，但它仍然不起作用。我不明白的是为什么主类中的变量不能在数据库类中使用。

Main.java

package com.healthix;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
    // write your code here

        CollectData instance1 =  new CollectData("James", "Minion", "None","Urine Test","Critical",'M',"22/03/1994","14/05/2019",54789631,25,69,true,true);
        String firstname = instance1.getFirstName();
        String lastname = instance1.getLastName();
        String notes = instance1.getNotes();
        String test = instance1.getTest();
        String refferalReason = instance1.getRefferalReason();
        char gender = instance1.getGender();
        String dateOfBirth = instance1.getDateOfBirth();
        String testDate = instance1.getTestDate();
        int nationalId = instance1.getNationalId();
        int subjectNumber = instance1.getSubjectNumber();
        int result = instance1.getResult();
        boolean resultFromAnalyzer = instance1.isResultFromAnalyzer();
        boolean acceptAsIs = instance1.isAcceptAsIs();
        Database db = new Database();
        db.connectDatabase();
    }


}

数据库.java

package com.healthix;

import java.sql.*;

public class Database {

    public Database() {
        connectDatabase();
    }

    public void connectDatabase() {

        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/hospitalapi", "root", "");
            Statement stmt = null;
            try {
                stmt = con.createStatement();
            } catch (SQLException e) {
                e.printStackTrace();
            }

        stmt.executeUpdate("insert into Patient(lastname,firstname,notes,test,refferalreason, gender,dateOfBirth,testDate,nationalId,subjectNumber,result,resultFromAnalyzer,acceptAsIs) " +
                    "values(lastname,firstname,notes,test,refferalReason,gender,dateOfBirth,testDate,nationalId,subjectNumber,result,resultFromAnalyzer,acceptAsIs)");


        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();

        }
    }
}

收集数据.java

package com.healthix;

public class CollectData {

    private String lastName, firstName, notes, test, refferalReason;
    private char gender;
    private String dateOfBirth, testDate;
    private int nationalId = 0, subjectNumber, result;
    private boolean resultFromAnalyzer, acceptAsIs;

    public CollectData(String lastName, String firstName, String notes, String test, String refferalReason, char gender, String dateOfBirth, String testDate, int nationalId, int subjectNumber, int result, boolean resultFromAnalyzer, boolean acceptAsIs) {
        this.lastName = lastName;
        this.firstName = firstName;
        this.notes = notes;
        this.test = test;
        this.refferalReason = refferalReason;
        this.gender = gender;
        this.dateOfBirth = dateOfBirth;
        this.testDate = testDate;
        this.nationalId = nationalId;
        this.subjectNumber = subjectNumber;
        this.result = result;
        this.resultFromAnalyzer = resultFromAnalyzer;
        this.acceptAsIs = acceptAsIs;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getNotes() {
        return notes;
    }

    public void setNotes(String notes) {
        this.notes = notes;
    }

    public String getTest() {
        return test;
    }

    public void setTest(String test) {
        this.test = test;
    }

    public String getRefferalReason() {
        return refferalReason;
    }

    public void setRefferalReason(String refferalReason) {
        this.refferalReason = refferalReason;
    }

    public char getGender() {
        return gender;
    }

    public void setGender(char gender) {
        this.gender = gender;
    }

    public String getDateOfBirth() {
        return dateOfBirth;
    }

    public void setDateOfBirth(String dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }

    public String getTestDate() {
        return testDate;
    }

    public void setTestDate(String testDate) {
        this.testDate = testDate;
    }

    public int getNationalId() {
        return nationalId;
    }

    public void setNationalId(int nationalId) {
        this.nationalId = nationalId;
    }

    public int getSubjectNumber() {
        return subjectNumber;
    }

    public void setSubjectNumber(int subjectNumber) {
        this.subjectNumber = subjectNumber;
    }

    public int getResult() {
        return result;
    }

    public void setResult(int result) {
        this.result = result;
    }

    public boolean isResultFromAnalyzer() {
        return resultFromAnalyzer;
    }

    public void setResultFromAnalyzer(boolean resultFromAnalyzer) {
        this.resultFromAnalyzer = resultFromAnalyzer;
    }

    public boolean isAcceptAsIs() {
        return acceptAsIs;
    }

    public void setAcceptAsIs(boolean acceptAsIs) {
        this.acceptAsIs = acceptAsIs;
    }
}

Answer 1

正如我被告知的那样，我检查了PreparedStatement 并意识到我的参数不在SQL 语句中。这就是为什么它没有任何东西可以传递到数据库中。这非常有帮助。这是代码。我还必须将 CollectData.java 的实例添加到 Database.java 中。这就是您访问 main 方法中传递的参数的方式。这是最终的代码和有用的资源。

https://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html#create_ps

import java.sql.*;

public class Database {
    CollectData instance1;

    public Database(CollectData instance1) {
        this.instance1 = instance1;

        connectDatabase();
    }

    public void connectDatabase() {

        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/hospitalapi", "root", "");
            String loadData = "insert into Patient(lastname,firstname,notes,test,refferalreason, gender,dateOfBirth,testDate,nationalId,subjectNumber,result,resultFromAnalyzer,acceptAsIs) " +
                    "values(?,?,?,?,?,?,?,?,?,?,?,?,?)";
            PreparedStatement updateData = con.prepareStatement(loadData);
            updateData.setString(1,instance1.getLastName());
            updateData.setString(2,instance1.getFirstName());
            updateData.setString(3,instance1.getNotes());
            updateData.setString(4,instance1.getTest());
            updateData.setString(5,instance1.getRefferalReason());
            updateData.setString(6,instance1.getGender());
            updateData.setString(7, instance1.getDateOfBirth());
            updateData.setString(8, instance1.getTestDate());
            updateData.setInt(9,instance1.getNationalId());
            updateData.setInt(10, instance1.getSubjectNumber());
            updateData.setInt(11, instance1.getResult());
            updateData.setBoolean(12, instance1.isResultFromAnalyzer());
            updateData.setBoolean(13, instance1.isAcceptAsIs());

        updateData.executeUpdate();


        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();

        }
    }
}