stmt.setInt(1, Integer.parseInt(input));

这段代码是用于设置 PreparedStatement 的参数值。其中，setInt() 方法用于设置参数的数据类型为整型，第一个参数表示参数的索引位置，第二个参数表示参数的值，这里是将字符串类型的 input 转换为整型。一般情况下，这个 PreparedStatement 对象会在执行 SQL 语句之前被创建，并通过设置参数值来填充 SQL 语句中的占位符，以便执行查询、更新或删除操作。

相关问题

<% //连接数据库 String driver = "com.mysql.jdbc.Driver"; String url = "jdbc:mysql://localhost:3306/votedb?serverTimezone=UTC&characterEncoding=UTF-8"; String username = "root"; String password = "123456"; Connection conn = null; Statement stmt = null; ResultSet rs = null; try { Class.forName(driver); conn = DriverManager.getConnection(url, username, password); stmt = conn.createStatement(); rs = stmt.executeQuery("SELECT * FROM vote"); while(rs.next()){ String title = rs.getString("title"); %> <input type="radio" name="option" value="<%=title%>"><%=title%><br> <% } } catch (Exception e) { e.printStackTrace(); } finally { //关闭连接 try { if (rs != null) { rs.close(); } if (stmt != null) { stmt.close(); } if (conn != null) { conn.close(); } } catch (SQLException e) { e.printStackTrace(); } } %> <a href="showVote.jsp">提交投票</a>选中后数据库数据变化

根据您的代码，您想要实现的功能是：在页面上展示投票选项列表（从数据库中查询出来），用户在选中一个选项后，点击“提交投票”按钮，将投票结果存储到数据库中。

您想要实现的选中后数据库数据变化，可能是指将用户的投票结果存储到数据库中。在提交投票的页面中，您可以编写一个表单，其中包含一个隐藏的投票ID字段和一个单选框选项，用户选中后提交表单。后台代码根据投票ID和选中的选项，将投票结果存储到数据库中。

这里提供一个简单的代码示例：

1. 提交投票页面（submitVote.jsp）：

<form action="voteHandler.jsp" method="post">
  <%  // 根据你的数据库结构修改以下代码
      String driver = "com.mysql.jdbc.Driver";
      String url = "jdbc:mysql://localhost:3306/votedb?serverTimezone=UTC&characterEncoding=UTF-8";
      String username = "root";
      String password = "123456";
      Connection conn = null;
      Statement stmt = null;
      ResultSet rs = null;
      try {
          Class.forName(driver);
          conn = DriverManager.getConnection(url, username, password);
          stmt = conn.createStatement();
          rs = stmt.executeQuery("SELECT * FROM vote");
          while(rs.next()){
              int id = rs.getInt("id");
              String title = rs.getString("title");
  %>
  <input type="radio" name="option" value="<%=id%>"><%=title%><br>
  <%    }
      } catch (Exception e) {
          e.printStackTrace();
      }
      finally {
          //关闭连接
          try {
              if (rs != null) {
                  rs.close();
              }
              if (stmt != null) {
                  stmt.close();
              }
              if (conn != null) {
                  conn.close();
              }
          } catch (SQLException e) {
              e.printStackTrace();
          }
      }
  %>
  <input type="hidden" name="voteId" value="<%=voteId%>">
  <input type="submit" value="提交投票">
</form>

2. 处理投票请求（voteHandler.jsp）：

<%  // 获取用户选择的选项和投票ID
    String option = request.getParameter("option");
    String voteId = request.getParameter("voteId");
    // 根据你的数据库结构修改以下代码
    String driver = "com.mysql.jdbc.Driver";
    String url = "jdbc:mysql://localhost:3306/votedb?serverTimezone=UTC&characterEncoding=UTF-8";
    String username = "root";
    String password = "123456";
    Connection conn = null;
    PreparedStatement pstmt = null;
    try {
        Class.forName(driver);
        conn = DriverManager.getConnection(url, username, password);
        pstmt = conn.prepareStatement("INSERT INTO vote_result(vote_id, option_id) VALUES (?, ?)");
        pstmt.setInt(1, Integer.parseInt(voteId));
        pstmt.setInt(2, Integer.parseInt(option));
        pstmt.executeUpdate();
    } catch (Exception e) {
        e.printStackTrace();
    }
    finally {
        //关闭连接
        try {
            if (pstmt != null) {
                pstmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    response.sendRedirect("voteResult.jsp?voteId=" + voteId); // 投票成功后跳转到投票结果页面
%>

3. 投票结果页面（voteResult.jsp）：

<%  // 获取投票ID并查询投票选项和结果
    String voteId = request.getParameter("voteId");
    // 根据你的数据库结构修改以下代码
    String driver = "com.mysql.jdbc.Driver";
    String url = "jdbc:mysql://localhost:3306/votedb?serverTimezone=UTC&characterEncoding=UTF-8";
    String username = "root";
    String password = "123456";
    Connection conn = null;
    Statement stmt = null;
    ResultSet rs = null;
    try {
        Class.forName(driver);
        conn = DriverManager.getConnection(url, username, password);
        stmt = conn.createStatement();
        rs = stmt.executeQuery("SELECT v.title, o.title AS option_title, COUNT(*) AS vote_count FROM vote v LEFT JOIN vote_option o ON v.id = o.vote_id LEFT JOIN vote_result r ON o.id = r.option_id WHERE v.id = " + voteId + " GROUP BY o.id");
        while(rs.next()){
            String title = rs.getString("title");
            String optionTitle = rs.getString("option_title");
            int voteCount = rs.getInt("vote_count");
%>
<p><%=optionTitle %>： <%=voteCount %> 票</p>
<%
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    finally {
        //关闭连接
        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
%>

希望这个示例能够帮助您完成您的需求。

1.创建Person类，Person的属性有： Strng name 姓名 String sex 性别 Integer age 年龄, String idNo 身份证号 Boolean isMerried 是否已婚 请生成相应的getter、setter方法。请编写注解@Label，表示所注解对象的中文名称，请把@Label注解标注在Person类和Person的每个属性上面。请编写PersonInput类，负责提示录入人员的相关属性，提示必须是注解@Label所标注的中文名称。请编写PersonDisplay，负责显示人员信息，显示时的属性名称必须为注解@Label所标注的中文名称，PersonInput类与PersonDisplay类实现了共同的接口PersonAction，接口PersonAction有方法process，方法process的签名为：public Person process(Person person); 2.在第一题目的基础上，编写注解@Column,属性有Label 表示类的属性的显示名称，Nullable 表示是否允许属性值为空，MaxLength 表示文本属性的最大长度，MinLength表示文本属性的最小长度，MaxValue表示最大值，MinValue表示最小值，把注解@Column加在Person类的每个属性上，在输入Person时根据注解@Column的配置进行校验。第一题的@Label只标注在类上。根据注解生成Person类对应的数据库表创建语句，以及生成数据库表的删除、新增、修改SQL语句。 并利用JDBC，实现数据库操作。只生成第二题代码

先给出完整代码，再一步步解释。

import java.lang.annotation.*;
import java.util.Scanner;

public class PersonInput implements PersonAction {
    private static Scanner input = new Scanner(System.in);

    @Override
    public Person process(Person person) {
        Class cls = person.getClass();
        Field[] fields = cls.getDeclaredFields();
        for (Field field : fields) {
            boolean isAccess = field.isAccessible();
            if (!isAccess) {
                field.setAccessible(true);
            }
            Label label = field.getAnnotation(Label.class);
            Column column = field.getAnnotation(Column.class);
            if (label != null) {
                System.out.print(label.value() + ": ");
            }
            if (column != null) {
                String inputStr = input.nextLine();
                if (!column.nullable() && (inputStr == null || inputStr.length() == 0)) {
                    System.out.println(column.label() + "不能为空");
                    inputStr = input.nextLine();
                }
                if (column.maxLength() > 0 && inputStr.length() > column.maxLength()) {
                    System.out.println(column.label() + "长度不能超过" + column.maxLength() + "个字符");
                    inputStr = input.nextLine();
                }
                if (column.minLength() > 0 && inputStr.length() < column.minLength()) {
                    System.out.println(column.label() + "长度不能少于" + column.minLength() + "个字符");
                    inputStr = input.nextLine();
                }
                if (column.maxValue() > Long.MIN_VALUE) {
                    long value = Long.parseLong(inputStr);
                    if (value > column.maxValue()) {
                        System.out.println(column.label() + "不能大于" + column.maxValue());
                        inputStr = input.nextLine();
                    }
                }
                if (column.minValue() < Long.MAX_VALUE) {
                    long value = Long.parseLong(inputStr);
                    if (value < column.minValue()) {
                        System.out.println(column.label() + "不能小于" + column.minValue());
                        inputStr = input.nextLine();
                    }
                }
                try {
                    if (field.getType() == String.class) {
                        field.set(person, inputStr);
                    } else if (field.getType() == Integer.class) {
                        int value = Integer.parseInt(inputStr);
                        field.set(person, value);
                    } else if (field.getType() == Long.class) {
                        long value = Long.parseLong(inputStr);
                        field.set(person, value);
                    } else if (field.getType() == Boolean.class) {
                        boolean value = Boolean.parseBoolean(inputStr);
                        field.set(person, value);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            if (!isAccess) {
                field.setAccessible(false);
            }
        }
        return person;
    }
}

import java.lang.annotation.*;

public class PersonDisplay implements PersonAction {
    @Override
    public Person process(Person person) {
        Class cls = person.getClass();
        Field[] fields = cls.getDeclaredFields();
        for (Field field : fields) {
            boolean isAccess = field.isAccessible();
            if (!isAccess) {
                field.setAccessible(true);
            }
            Label label = field.getAnnotation(Label.class);
            if (label != null) {
                try {
                    System.out.println(label.value() + ": " + field.get(person));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            if (!isAccess) {
                field.setAccessible(false);
            }
        }
        return person;
    }
}

@Target({ElementType.TYPE, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@interface Label {
    String value();
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Column {
    String label();

    boolean nullable() default true;

    int maxLength() default 0;

    int minLength() default 0;

    long maxValue() default Long.MIN_VALUE;

    long minValue() default Long.MAX_VALUE;
}

interface PersonAction {
    Person process(Person person);
}

class Person {
    @Label("姓名")
    @Column(label = "姓名", nullable = false, maxLength = 32)
    private String name;

    @Label("性别")
    @Column(label = "性别")
    private String sex;

    @Label("年龄")
    @Column(label = "年龄", minValue = 0, maxValue = 200)
    private Integer age;

    @Label("身份证号")
    @Column(label = "身份证号", maxLength = 18)
    private String idNo;

    @Label("是否已婚")
    @Column(label = "是否已婚")
    private Boolean isMarried;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getIdNo() {
        return idNo;
    }

    public void setIdNo(String idNo) {
        this.idNo = idNo;
    }

    public Boolean getMarried() {
        return isMarried;
    }

    public void setMarried(Boolean married) {
        isMarried = married;
    }
}

public class Main {
    private static final String CREATE_TABLE_SQL = "CREATE TABLE `person` (\n" +
            "  `id` int(11) NOT NULL AUTO_INCREMENT,\n" +
            "  `name` varchar(32) NOT NULL,\n" +
            "  `sex` varchar(8) DEFAULT NULL,\n" +
            "  `age` int(11) DEFAULT NULL,\n" +
            "  `id_no` varchar(18) DEFAULT NULL,\n" +
            "  `married` tinyint(1) DEFAULT NULL,\n" +
            "  PRIMARY KEY (`id`)\n" +
            ") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;";

    private static final String DROP_TABLE_SQL = "DROP TABLE IF EXISTS `person`;";

    private static final String INSERT_SQL = "INSERT INTO `person` (`name`, `sex`, `age`, `id_no`, `married`) VALUES (?, ?, ?, ?, ?);";

    private static final String UPDATE_SQL = "UPDATE `person` SET `name`=?,`sex`=?,`age`=?,`id_no`=?,`married`=? WHERE `id`=?;";

    private static final String DELETE_SQL = "DELETE FROM `person` WHERE `id`=?;";

    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8", "root", "123456");
            Statement stmt = conn.createStatement();
            stmt.executeUpdate(DROP_TABLE_SQL);
            stmt.executeUpdate(CREATE_TABLE_SQL);

            PersonInput input = new PersonInput();
            PersonDisplay display = new PersonDisplay();
            Person person = new Person();
            input.process(person);
            display.process(person);

            ps = conn.prepareStatement(INSERT_SQL);
            ps.setString(1, person.getName());
            ps.setString(2, person.getSex());
            ps.setInt(3, person.getAge());
            ps.setString(4, person.getIdNo());
            ps.setBoolean(5, person.getMarried());
            ps.executeUpdate();

            ps = conn.prepareStatement(UPDATE_SQL);
            ps.setString(1, person.getName());
            ps.setString(2, person.getSex());
            ps.setInt(3, person.getAge());
            ps.setString(4, person.getIdNo());
            ps.setBoolean(5, person.getMarried());
            ps.setInt(6, 1);
            ps.executeUpdate();

            ps = conn.prepareStatement(DELETE_SQL);
            ps.setInt(1, 1);
            ps.executeUpdate();

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (ps != null) {
                    ps.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

首先，我们定义了两个注解，@Label和@Column。其中，@Label是用来给类和属性添加中文名称的，@Column是用来给属性添加数据库字段的一些配置信息的。

@Target({ElementType.TYPE, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@interface Label {
    String value();
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Column {
    String label();

    boolean nullable() default true;

    int maxLength() default 0;

    int minLength() default 0;

    long maxValue() default Long.MIN_VALUE;

    long minValue() default Long.MAX_VALUE;
}

然后，我们定义了一个Person类，它有姓名、性别、年龄、身份证号、是否已婚等属性，每个属性都添加了@Label和@Column注解。我们使用注解处理器，可以根据@Column注解的配置信息来进行输入校验，这样就可以避免输入错误的数据。同时，我们还定义了PersonInput和PersonDisplay两个类，它们都实现了PersonAction接口，分别用于输入和输出一个Person对象。

class Person {
    @Label("姓名")
    @Column(label = "姓名", nullable = false, maxLength = 32)
    private String name;

    @Label("性别")
    @Column(label = "性别")
    private String sex;

    @Label("年龄")
    @Column(label = "年龄", minValue = 0, maxValue = 200)
    private Integer age;

    @Label("身份证号")
    @Column(label = "身份证号", maxLength = 18)
    private String idNo;

    @Label("是否已婚")
    @Column(label = "是否已婚")
    private Boolean isMarried;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getIdNo() {
        return idNo;
    }

    public void setIdNo(String idNo) {
        this.idNo = idNo;
    }

    public Boolean getMarried() {
        return isMarried;
    }

    public void setMarried(Boolean married) {
        isMarried = married;
    }
}

interface PersonAction {
    Person process(Person person);
}

public class PersonInput implements PersonAction {
    @Override
    public Person process(Person person) {
        Class cls = person.getClass();
        Field[] fields = cls.getDeclaredFields();
        for (Field field : fields) {
            boolean isAccess = field.isAccessible();
            if (!isAccess) {
                field.setAccessible(true);
            }
            Label label = field.getAnnotation(Label.class);
            Column column = field.getAnnotation(Column.class);
            if (label != null) {
                System.out.print(label.value() + ": ");
            }
            if (column != null) {
                String inputStr = input.nextLine();
                if (!column.nullable() && (inputStr == null || inputStr.length() == 0)) {
                    System.out.println(column.label() + "不能为空");
                    inputStr = input.nextLine();
                }
                if (column.maxLength() > 0 && inputStr.length() > column.maxLength()) {
                    System.out.println(column.label() + "长度不能超过" + column.maxLength() + "个字符");
                    inputStr = input.nextLine();
                }
                if (column.minLength() > 0 && inputStr.length() < column.minLength()) {
                    System.out.println(column.label() + "长度不能少于" + column.minLength() + "个字符");
                    inputStr = input.nextLine();
                }
                if (column.maxValue() > Long.MIN_VALUE) {
                    long value = Long.parseLong(inputStr);
                    if (value > column.maxValue()) {
                        System.out.println(column.label() + "不能大于" + column.maxValue());
                        inputStr = input.nextLine();
                    }
                }
                if (column.minValue() < Long.MAX_VALUE) {
                    long value = Long.parseLong(inputStr);
                    if (value < column.minValue()) {
                        System.out.println(column.label() + "不能小于" + column.minValue());
                        inputStr = input.nextLine();
                    }
                }
                try {
                    if (field.getType() == String.class) {
                        field.set(person, inputStr);
                    } else if (field.getType() == Integer.class) {
                        int value = Integer.parseInt(inputStr);
                        field.set(person, value);
                    } else if (field.getType() == Long.class) {
                        long value = Long.parseLong(inputStr);
                        field.set(person, value);
                    } else if (field.getType() == Boolean.class) {
                        boolean value = Boolean.parseBoolean(inputStr);
                        field.set(person, value);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            if (!isAccess) {
                field.setAccessible(false);
            }
        }
        return person;
    }
}

public class PersonDisplay implements PersonAction {
    @Override
    public Person process(Person person) {
        Class cls = person.getClass();
        Field[] fields = cls.getDeclaredFields();
        for (Field field : fields) {
            boolean isAccess = field.isAccessible();
            if (!isAccess) {
                field.setAccessible(true);
            }
            Label label = field.getAnnotation(Label.class);
            if (label != null) {
                try {
                    System.out.println(label.value() + ": " + field.get(person));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            if (!isAccess) {
                field.setAccessible(false);
            }
        }
        return person;
    }
}

最后，我们在Main类中使用JDBC，将Person对象保存到数据库中。在保存之前，先执行了一次删除表和创建表的操作。

public class Main {
    private static final String CREATE_TABLE_SQL = "CREATE TABLE `person` (\n" +
            "  `id` int(11) NOT NULL AUTO_INCREMENT,\n" +
            "  `name` varchar(32) NOT NULL,\n" +
            "  `sex` varchar(8) DEFAULT NULL,\n" +
            "  `age` int(11) DEFAULT NULL,\n" +
            "  `id_no` varchar(18) DEFAULT NULL,\n" +
            "  `married` tinyint(1) DEFAULT NULL,\n" +
            "  PRIMARY KEY (`id`)\n" +
            ") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;";

    private static final String DROP_TABLE_SQL = "DROP TABLE IF EXISTS `person`;";

    private static final String INSERT_SQL = "INSERT INTO `person` (`name`, `sex`, `age`, `id_no`, `married`) VALUES (?, ?, ?, ?, ?);";

    private static final String UPDATE_SQL = "UPDATE `person` SET `name`=?,`sex`=?,`age`=?,`id_no`=?,`married`=? WHERE `id`=?;";

    private static final String DELETE_SQL = "DELETE FROM `person` WHERE `id`=?;";

    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8", "root", "123456");
            Statement stmt = conn.createStatement();
            stmt.executeUpdate(DROP_TABLE_SQL);
            stmt.executeUpdate(CREATE_TABLE_SQL);

            PersonInput input = new PersonInput();
            PersonDisplay display = new PersonDisplay();
            Person person = new Person();
            input.process(person);
            display.process(person);

            ps = conn.prepareStatement(INSERT_SQL);
            ps.setString(1, person.getName());
            ps.setString(2, person.getSex());
            ps.setInt(3, person.getAge());
            ps.setString(4, person.getIdNo());
            ps.setBoolean(5, person.getMarried());
            ps.executeUpdate();

            ps = conn.prepareStatement(UPDATE_SQL);
            ps.setString(1, person.getName());
            ps.setString(2, person.getSex());
            ps.setInt(3, person.getAge());
            ps.setString(4, person.getIdNo());
            ps.setBoolean(5, person.getMarried());
            ps.setInt(6, 1);
            ps.executeUpdate();

            ps = conn.prepareStatement(DELETE_SQL);
            ps.setInt(1, 1);