看了以前写的代码，对就是下面这个
觉得以前写的代码好烂啊！！！，重新理了一下思路，写得更规范和简练，应该效率也会高很多，用了一下下午写的连接池（半废品。。。）
下面直接上代码，代码很好理解，就是用了简单的反射，注解的部分我都写了注释
package jdbc;
import util.StringUtil;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
public class DataUtil {
public static int excuteUpdate(String sql, Object... objects) {
Connection connection = ConnectionPool.getInstance().getCurrentConnection();
PreparedStatement preparedStatement = null;
try {
preparedStatement = getStateMent(connection, sql, objects);
return preparedStatement.executeUpdate(); //执行sql并返回结果
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (preparedStatement != null) {
try {
preparedStatement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
return 0;
}
/**
* 查询单挑记录
*
* @param sql 查询语句
* @param clazz 返回对象的class
* @param objects 需要的参数，必须跟sql占位符的位置一一对应
* @param <T> 泛型返回
* @return 返回单个对象
*/
public static <T> T queryForObject(String sql, Class<T> clazz, Object... objects) {
Connection connection = ConnectionPool.getInstance().getCurrentConnection();
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
T object = null;
try {
preparedStatement = getStateMent(connection, sql, objects);
resultSet = getResultSet(preparedStatement);
if (resultSet.next()) {
object = invokeObject(resultSet, clazz);
}
} catch (SQLException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} finally {
close(preparedStatement, resultSet); //记得关闭
}
return object;
}
/**
*查询多条记录
*
* @param sql 查询语句
* @param clazz 返回对象的class
* @param objects 需要的参数，必须跟sql占位符的位置一一对应
* @param <T> 泛型返回
*
* @return list
*/
public static <T> List<T> queryForList(String sql, Class<T> clazz, Object... objects) {
Connection connection = ConnectionPool.getInstance().getCurrentConnection();
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
List<T> list = new ArrayList<T>();
try {
preparedStatement = getStateMent(connection, sql, objects);
resultSet = getResultSet(preparedStatement);
while (resultSet.next()) {
list.add(invokeObject(resultSet, clazz));
}
} catch (SQLException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} finally {
close(preparedStatement, resultSet);
}
return list.size() > 0 ? list : null;
}
private static void close(PreparedStatement preparedStatement, ResultSet resultSet) {
try {
if (preparedStatement != null) {
preparedStatement.close();
resultSet.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
private static <T> T invokeObject(ResultSet resultSet, Class<T> clazz) throws IllegalAccessException, InstantiationException,
SQLException, NoSuchFieldException, NoSuchMethodException, InvocationTargetException {
T object = clazz.newInstance();
ResultSetMetaData metaData = resultSet.getMetaData();
for (int i = 0, count = metaData.getColumnCount(); i < count; i++) {
String columnName = metaData.getColumnName(i + 1); //数据库返回结果的列名
String fieldName = StringUtil.camelName(columnName); //去掉列名中的下划线“_”并转为驼峰命名
Field field = clazz.getDeclaredField(fieldName); //根据字段名获取field
String methName = setMethodName(fieldName); //拼set方法名
Class type = field.getType(); //获取字段类型
Method setMethod = clazz.getDeclaredMethod(methName, field.getType());
Object value = resultSet.getObject(i + 1); //获取字段值
setMethod.invoke(object, type.cast(value)); //强转并且赋值
}
return object;
}
private static PreparedStatement getStateMent(Connection connection, String sql, Object... objects) throws SQLException {
if (connection == null) {
return null;
}
PreparedStatement preparedStatement = connection.prepareStatement(sql);
for (int i = 0, len = objects.length; i < len; i++) {
preparedStatement.setObject(i + 1, objects[i]); //给sql每个？占位符填上数据
}
return preparedStatement;
}
private static ResultSet getResultSet(PreparedStatement statement) throws SQLException {
if (statement == null) {
return null;
} else {
return statement.executeQuery();
}
}
private static String setMethodName(String str) {
return "set" + StringUtil.firstUpperCase(str);
}
}
用到了几个简单的字符串处理方法
package util;
public class StringUtil {
/**
* 转为驼峰命名
* @param str
* @return string
*/
public static String camelName(String str) {
if (!isEmpty(str)) {
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0, len = str.length(); i < len; i++) {
if (str.charAt(i) == '_') {
while (str.charAt(i + 1) == '_') {
i++;
}
stringBuilder.append(("" + str.charAt(++i)).toUpperCase());
} else {
stringBuilder.append(str.charAt(i));
}
}
return stringBuilder.toString();
}
return str;
}
/**
* 判断是否为空串
*
* @param str
* @return
*/
public static boolean isBlank(String str) {
if (str != null && str.length() > 0) {
for (int i = 0, len = str.length(); i < len; i++) {
if (!Character.isSpaceChar(str.charAt(i))) {
return false;
}
}
}
return true;
}
/**
* 判断是否为空串 ？！！！ 我怎么又写了个一样的方法？！！！
* @param str
* @return
*/
public static boolean isEmpty(String str) {
return str == null || str.length() == 0;
}
/**
* 将第一个字母替换为大写
* @param str
* @return
*/
public static String firstUpperCase(String str) {
return str.substring(0, 1).toUpperCase() + str.substring(1, str.length());
}
}
下面开始是测试了
首先数据库
然后测试类，跟表结构对应的
package po;
import java.util.Date;
public class User {
private Integer id;
private Integer age;
private String name;
private Double score;
private Date createTime;
private Date updateTime;
//set、get 方法均省略了，但是这个是必须的
｝
测试代码
import java.util.List;
public class Test {
public static void main(String[] args) {
String sql = "select * from t_user";
List<User> list = DataUtil.queryForList(sql,User.class);
System.out.println("查询多条记录：" + list);
System.out.println("******************************************************************");
sql = "select * from t_user where id = ?";
User user = DataUtil.queryForObject(sql,User.class,1);
System.out.println("查询单条记录：" + user);
System.out.println("******************************************************************");
sql = "insert into t_user(name,score,create_time,update_time) values(?,?,now(),now())";
int t = DataUtil.excuteUpdate(sql,"大牛",66.66);
System.out.println("执行插入操作结果："+t);
}
}
测试结果
太晚了，先到这了，有空把我的mybatis和ioc容器也瞎j8重写一下
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