Question

我想使用java创建类似任务管理器的东西。我决定使用PostgreSQL来保存我的任务。在这一刻，我想将我创建的任务保存到PostgreSQL，为此我有以下代码：

package TaskMgr;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.util.Locale;
public class Task {

private String title;
private String description;
private LocalDate dateFormat;


public Task(String title, String description, String date) {
    this.title = title;
    this.description = description;
    this.dateFormat = setDate(date);
}


public LocalDate setDate(String inputDate) {
    DateTimeFormatter formatter = new DateTimeFormatterBuilder()
            .parseCaseInsensitive()
            .appendPattern("yyyy-MM-d")
            .toFormatter(Locale.ENGLISH);
    formatter = formatter.withLocale(Locale.ENGLISH);
    LocalDate outputDate = LocalDate.parse(inputDate, formatter);
    return outputDate;

}

public String getTitle() {
    return title;
}

public String getDescription() {
    return description;
}


public LocalDate getDateFormat() {
    return dateFormat;
}

public static void main(String[] args) {

}


}

我的数据库代码:(已创建表任务的数据库，包含字段：文本类型的标题，文本类型的描述和日期类型的日期）。这是数据库类的代码：

package TaskMgr;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.time.LocalDate;
import java.time.Month;

public class Database {

private final String url = "jdbc:postgresql://localhost/tasksdb";
private final String user = "postgres";
private final String password = "31415926";

public Connection connect() {
    Connection conn = null;
    try {
        conn = DriverManager.getConnection(url, user, password);
        System.out.println("Connected to the PostgreSQL server successfully.");

    } catch (SQLException e) {
        System.out.println(e.getMessage());
    }

    return conn;
}

public void createItem(int idCur, String title, String description, LocalDate date) {
    try {
        Statement stmnt = null;
        stmnt = connect().createStatement();
        String sql = "INSERT INTO TASKS (ID,TITLE,DESCRIPTION,DATE) "
                + "VALUES " + "(" + idCur + ", " + title + ", " + description + ", " + date + ")";
        stmnt.executeUpdate(sql);

    } catch (SQLException e) {
        System.out.println(e.getMessage());
    }

}

public static void main(String[] args) {
    Database database = new Database();
    database.connect();
    Task task = new Task("'Test2'", "'Test2 description'", "1998-01-07");
    database.createItem(2, task.getTitle(), task.getDescription(), task.getDateFormat());

}

}

但是Intellij引发了以下错误：

ERROR: column "date" is of type date but expression is of type integer
TIP: You will need to rewrite or cast the expression.

我试图谷歌这个错误，但没有任何帮助。我该怎么办？约会？

Answer 1

您应该在这里使用预准备语句，这样可以解决在构建查询时不知道要使用的确切格式的问题。

PreparedStatement st = conn.prepareStatement("INSERT INTO TASKS (ID, TITLE, DESCRIPTION, DATE) VALUES (?, ?, ?, ?)");
st.setInt(1, idCur);
st.setString(2, title);
st.setString(3, description);
st.setObject(4, date);
st.executeUpdate();
st.close();

准备好的语句负责确保INSERT语句将以正确的格式为Postgres数据库使用日期和时间戳文字。

除此之外，预准备语句还可以保护您的代码免受SQL注入攻击。以下是Postgres的JDBC驱动程序文档的链接：

https://jdbc.postgresql.org/documentation/head/

使用JDBC将值插入postgresql

1 个答案: