對於C（建立），U（更新），D（刪除）都屬於更新操作，對於R（讀取查詢）屬於查詢操作。這裡編寫兩個通用的更新和查詢方法。

更新

更新簡單，只需要傳入對應的sql和sql的佔位符，然後執行更新就可以了。

/**
     * @return 返回影響的行數
     * @param connection
     * @param sql
     * @param args
     */
    public int update(String sql, Object... args) {
        int row = 0;
        try {
            Connection connection = JDBCUtils.getConnection();
            PreparedStatement preparedStatement = connection
                    .prepareStatement(sql);
            // 填充sql的佔位符
 

            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }
            row = preparedStatement.executeUpdate();
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return
 
 row;
    }

查詢

對於查詢，比較麻煩的是，返回的結果集的處理，可以遍歷結果集然後建立對應的javabean，然後返回。但是對於不同的javabean，對應的屬性並不知道，這裡可以從結果集中獲取查詢結果的別名（別名和javabean的屬性名對應），然後利用反射建立物件併為屬性賦相應的值，返回一個javabean的物件。

public <T> T query(Class<T> clazz, String sql, Object... args) {

        T entity = null;

        Connection connection = null
 
;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            // 獲取resultSet
            connection = JDBCUtils.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }
            resultSet = preparedStatement.executeQuery();
            // 獲取resultSetMetaData
            ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
            // 建立一個MAP 鍵 :SQL查詢得到的列的別名，別名和javaBean的屬性名對應 值:對應列的值
            Map<String, Object> values = new HashMap<String, Object>();

            // 處理結果集，利用resultSetMetaData填充Map
            while (resultSet.next()) {
                for (int i = 0; i < resultSetMetaData.getColumnCount(); i++) {
                    String columnLable = resultSetMetaData
                            .getColumnLabel(i + 1);
                    Object columnValue = resultSet.getObject(i + 1);

                    values.put(columnLable, columnValue);
                }
            }

            // 如果map不為空，利用反射建立物件
            if (values.size() > 0) {
                // 反射建立物件
                entity = clazz.newInstance();
                // 遍歷Map ,利用反射為屬性賦值
                for (Map.Entry<String, Object> entry : values.entrySet()) {
                    String fieldName = entry.getKey();
                    Object value = null;
                    // 因為java中和mysql中資料型別對應不一致
                    // mysql中int對應JAVA中的long，所以當查詢出int型資料的時候需要轉換
                    if (entry.getValue() instanceof Long) {
                        value = Integer.parseInt(entry.getValue().toString());
                    } else {
                        value = entry.getValue();
                    }
                    // ReflectionUtils.setFieldValue(entity, fieldName, value);
                    Field field = clazz.getDeclaredField(fieldName);
                    field.setAccessible(true);
                    field.set(entity, value);
                }

            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return entity;
    }

建立兩個javabean，對應資料庫中的表
user.java：

package com.aaa.entity;

import java.sql.Date;

public class User {

    private int userId;
    private String userName;
    private String userPassword;
    private Date userBirth;

    public User(int userId, String userName, String userPassword, Date userBirth) {
        super();
        this.userId = userId;
        this.userName = userName;
        this.userPassword = userPassword;
        this.userBirth = userBirth;
    }

    public User() {

    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPassword() {
        return userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }

    public Date getUserBirth() {
        return userBirth;
    }

    public void setUserBirth(Date userBirth) {
        this.userBirth = userBirth;
    }

    @Override
    public String toString() {
        return "User [userId=" + userId + ", userName=" + userName
                + ", userPassword=" + userPassword + ", userBirth=" + userBirth
                + "]";
    }

}

customer.java：

package com.aaa.entity;

public class Customer {
    private int customerId;
    private String customerName;
    private String customerPassword;

    public int getCustomerId() {
        return customerId;
    }

    public void setCustomerId(int customerId) {
        this.customerId = customerId;
    }

    public String getCustomerName() {
        return customerName;
    }

    public void setCustomerName(String customerName) {
        this.customerName = customerName;
    }

    public String getCustomerPassword() {
        return customerPassword;
    }

    public void setCustomerPassword(String customerPassword) {
        this.customerPassword = customerPassword;
    }

    public Customer(int customerId, String customerName, String customerPassword) {
        super();
        this.customerId = customerId;
        this.customerName = customerName;
        this.customerPassword = customerPassword;
    }

    public Customer() {
        super();
    }

    public String toString() {
        return "Customer [customerId=" + customerId + ", customerName="
                + customerName + ", customerPassword=" + customerPassword + "]";
    }

}

測試：

public void testQuery() {
        String sql = "SELECT user_id userId,user_name userName,user_password userPassword,user_birth userBirth FROM user WHERE user_id = ?";
        User user = query(User.class, sql, 2);
        System.out.println(user);

        sql = "SELECT customer_id customerId,customer_name customerName,customer_password customerPassword FROM customer WHERE customer_id = ? AND customer_name =?";
        Customer customer = query(Customer.class, sql, 2, "marry");
        System.out.println(customer);
    }

結果：

總結：在查詢的時候，只需要傳入sql和sql佔位符以及對應的class，就可以直接返回對應的物件，而不需要為每一個Javabean建立對應的方法。