Java Prepared语句不执行 [英] Java Prepared statement not executing

问题描述

我创建了一个小的3层程序，包括：前端 - > servlet - >数据库。

前端我在表单中输入一些细节。它们被传递给一个servlet，它将呈现一些HTML并显示输入到表单中的值，同时还调用了DatabaseHelper类。 DatabaseHelper然后连接并将这些相同的值插入到表中。

我知道这些值被传递给servlet类ok，因为它们显示在HTML中。所以问题必须在准备的语句。问题是，我看不到任何错误的语句本身。当我查询表本身时，没有数据。

数据库连接是功能性的，因为我可以使用硬编码语句将值插入数据库，而不是准备语句。

下面是使用语句Im。非常感谢任何建议。

  public void addRegisterDetails（String name，String email，String country，String password，）{
 try {
 String driver =com.mysql.jdbc.Driver; 
 Class.forName（driver）.newInstance（）; 
 //创建db连接
 con = DriverManager.getConnection（url，USERNAME，PASSWORD）; 
 st = con.createStatement（）; 
 
 
 String query =INSERT INTO user_information（name，email，country，password）+VALUES（？，？，？，？） 
 PreparedStatement preparedStmt = con.prepareStatement（query）; 
 preparedStmt.setString（1，name）; 
 preparedStmt.setString（2，电子邮件）; 
 preparedStmt.setString（3，country）; 
 preparedStmt.setString（4，password）; 
 preparedStmt.execute（）; 
 
} catch（ClassNotFoundException ex）{
 System.out.println（ex）; 
} catch（Exception e）{
 e.printStackTrace（）; 
} 
} 
  

表定义

---

id |名称|电子邮件|国家|

解决方案

p>您应该在语句对象上调用方法 executeUpdate（）。

任何调用提交数据，任何事务处理。如果你跳过这段代码的目的这个问题的很好;否则这是相当重要的一步（如果一切顺利，提交，回退异常情况）

I have created a small 3 tier program, consisting of : front end -> servlet -> database.

Front end I enter some details into a form. They are passed to a servlet, which will render some HTML and display the values entered into the form, while also calling a class DatabaseHelper. The DatabaseHelper then connects and inserts these same values into a table.

I know the values are being passed to the servlet class ok, as they are being displayed in the HTML. So the problem must lie within the prepared statement. Problem is, I cannot see any fault with the statement itself. When I query the table itself, there is no data there.

Database connectivity is functional, as I can insert values into a database using hardcoded statements, just not a prepared statement.

Here is a look at the statement Im using. Any advice is much appreciated.

    public void addRegisterDetails(String name, String email, String country, String password, ){
    try{ 
        String driver = "com.mysql.jdbc.Driver";    
        Class.forName(driver).newInstance();
        // Make db connection
        con = DriverManager.getConnection(url, USERNAME, PASSWORD);   
        st  = con.createStatement();


        String query = " INSERT INTO user_information (name, email, country, password)" + " VALUES (?, ?, ?, ?)";
        PreparedStatement preparedStmt = con.prepareStatement(query);
        preparedStmt.setString (1, name);
        preparedStmt.setString (2, email);
        preparedStmt.setString (3, country);
        preparedStmt.setString (4, password);
        preparedStmt.execute();

    }catch(ClassNotFoundException ex) {
        System.out.println(ex);
    }catch(Exception e){
         e.printStackTrace();
    }
}

Table definition

---

id| name | email | country | password

all VARCHAR except the id, which is type INT.

解决方案

You should invoke the method executeUpdate() on the statement object.

Also, I don't see any call to commit the data, any transaction handling. It's fine if you skipped that piece of code for the purpose of this question; otherwise it's quite an important step ( commit if all goes well, rollback for exception scenarios)

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