转自：
下文是笔者收集的关于操作数据库的工具类，如下所示:
操作数据库可以毫不夸张的说：“每个业务系统都少不了的操作”,
下文是笔者收集的支持Mysql、Oracle、Postgresql的分页查询 的一个数据库工具类，如下所示:
package com.java265.utils;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.Date;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Time;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.naming.NamingException;
import javax.sql.DataSource;
/**
* 数据库查询工具类
* 使用预编译的sql
*
* @author XueLiang
*
*/
public class DBUtil {
private static String driver;
private static DataSource ds = null;
private static String url = "jdbc:postgresql://192.168.56.101/db";
private static String user = "test";
private static String password = "*************";
static {
try {
Class.forName("org.postgresql.Driver");
//ds = (DataSource)SpringContextUtil.getBean("dataSource");
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 建立连接
*
* @return con Connection
* @throws Exception
*/
private static Connection getConnection() throws Exception {
Connection conn = DriverManager.getConnection(url, user, password);
// Connection conn = ds.getConnection();
Driver d = DriverManager.getDriver(conn.getMetaData().getURL());
driver = d.getClass().getName();
return conn;
}
/**
* 关闭连接
*
* @param conn
* @param stmt
* @param preStmt
* @param rs
* @throws SQLException
*/
private static void replease(Connection conn, Statement stmt, ResultSet rs) throws SQLException {
if (rs != null) {
rs.close();
rs = null;
}
if (stmt != null) {
stmt.close();
stmt = null;
}
if (conn != null) {
conn.close();
conn = null;
}
}
/**
* 利用正则表达式,获得SELECT SQL中的列名
*
* @param sql
* @return
*/
private static List getColumnsFromSelect(String sql) {
List colNames = new ArrayList();
// 取出sql中列名部分
Pattern p = Pattern.compile("(?i)select\\s(.*?)\\sfrom.*");
Matcher m = p.matcher(sql.trim());
String[] tempA = null;
if (m.matches()) {
tempA = m.group(1).split(",");
}
if (tempA == null) {
return null;
}
String p1 = "(\\w+)";
String p2 = "(?:\\w+\\s(\\w+))";
String p3 = "(?:\\w+\\sas\\s(\\w+))";
String p4 = "(?:\\w+\\.(\\w+))";
String p5 = "(?:\\w+\\.\\w+\\s(\\w+))";
String p6 = "(?:\\w+\\.\\w+\\sas\\s(\\w+))";
String p7 = "(?:.+\\s(\\w+))";
String p8 = "(?:.+\\sas\\s(\\w+))";
p = Pattern.compile("(?:" + p1 + "||" + p2 + "||" + p3 + "||" + p4
+ "||" + p5 + "||" + p6 + "||" + p7 + "||" + p8 + ")");
for (String temp : tempA) {
m = p.matcher(temp.trim());
if (!m.matches()) {
continue;
}
for (int i = 1; i <= m.groupCount(); i++) {
if (m.group(i) == null || "".equals(m.group(i))) {
continue;
}
colNames.add(m.group(i));
}
}
return colNames;
}
/**
* 利用正则表达式,获得INSERT SQL中的列名
*
* @param sql
* @return
*/
private static List getColumnsFromInsert(String sql) {
List colNames = new ArrayList();
// 取出sql中列名部分
Pattern p = Pattern.compile("(?i)insert\\s+into.*\\((.*)\\)\\s+values.*");
Matcher m = p.matcher(sql.trim());
String[] tempA = null;
if (m.matches()) {
tempA = m.group(1).split(",");
}
if (tempA == null) {
return null;
}
String p1 = "(\\w+)";
String p2 = "(?:\\w+\\s(\\w+))";
String p3 = "(?:\\w+\\sas\\s(\\w+))";
String p4 = "(?:\\w+\\.(\\w+))";
String p5 = "(?:\\w+\\.\\w+\\s(\\w+))";
String p6 = "(?:\\w+\\.\\w+\\sas\\s(\\w+))";
String p7 = "(?:.+\\s(\\w+))";
String p8 = "(?:.+\\sas\\s(\\w+))";
p = Pattern.compile("(?:" + p1 + "||" + p2 + "||" + p3 + "||" + p4
+ "||" + p5 + "||" + p6 + "||" + p7 + "||" + p8 + ")");
for (String temp : tempA) {
m = p.matcher(temp.trim());
if (!m.matches()) {
continue;
}
for (int i = 1; i <= m.groupCount(); i++) {
if (m.group(i) == null || "".equals(m.group(i))) {
continue;
}
colNames.add(m.group(i));
}
}
return colNames;
}
/**
* 利用正则表达式,获得UPDATE SQL中的列名, 包括WHERE字句的
*
* @param sql
* @return
*/
private static List getColumnsFromUpdate(String sql) {
List colNames = new ArrayList();
// 取出sql中列名部分
Pattern p = Pattern.compile("(?i)update(?:.*)set(.*)(?:from.*)*where(.*(and)*.*)");
Matcher m = p.matcher(sql.trim());
String[] tempA = null;
if (m.matches()) {
tempA = m.group(1).split(",");
if(m.groupCount() > 1){
String[] tmp = m.group(2).split("and");
String[] fina = new String[tempA.length + tmp.length];
System.arraycopy(tempA, 0, fina, 0, tempA.length);
System.arraycopy(tmp, 0, fina, tempA.length, tmp.length);
tempA = fina;
}
}
if (tempA == null) {
return null;
}
String p1 = "(?i)(\\w+)(?:\\s*\\=\\s*.*)";
String p2 = "(?i)(?:\\w+\\.)(\\w+)(?:\\s*\\=\\s*.*)";
p = Pattern.compile(p1 + "||" + p2);
for (String temp : tempA) {
m = p.matcher(temp.trim());
if (!m.matches()) {
continue;
}
for (int i = 1; i <= m.groupCount(); i++) {
if (m.group(i) == null || "".equals(m.group(i))) {
continue;
}
colNames.add(m.group(i));
}
}
return colNames;
}
/**
* 为sql添加统计代码
*
* @param sql
* @return
*/
private static String addCountSQL(String sql) {
StringBuffer sb = new StringBuffer();
sb.append(" select count(*) as dataCount from (");
sb.append(sql);
sb.append(") as a");
return sb.toString();
}
/**
* 为sql添加分页代码
*
* @param sql
* @param start
* @param limit
* @return
*/
private static String addPagingSQL(String sql, int start, int limit) {
StringBuffer sb = new StringBuffer();
if ("com.microsoft.jdbc.sqlserver.SQLServerDviver".equals(driver)) {//SQLServer 0.7 2000
} else if ("com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver)) {//SQLServer 2005 2008
} else if ("com.mysql.jdbc.Driver".equals(driver)) {//MySQL
sb.append(sql);
sb.append(" LIMIT ");
sb.append(start);
sb.append(",");
sb.append(limit);
} else if ("oracle.jdbc.driver.OracleDriver".equals(driver)) {//Oracle8/8i/9i/10g数据库（thin模式）
List list = getColumnsFromSelect(sql);
sb.append("select ");
for (String str : list)
sb.append(str).append(", ");
sb.deleteCharAt(sb.lastIndexOf(","));
sb.append(" from (").append(sql).append(") as a");
sb.append(" where rownum between ").append(start == 0 ? 1 : start).append(" and ").append(limit);
} else if ("com.ibm.db2.jdbc.app.DB2Driver".equals(driver)) {//DB2
} else if ("com.sybase.jdbc.SybDriver".equals(driver)) {//Sybase
} else if ("com.informix.jdbc.IfxDriver".equals(driver)) {//Informix
} else if ("org.postgresql.Driver".equals(driver)) {//PostgreSQL
sb.append(sql);
sb.append(" LIMIT ");
sb.append(limit);
sb.append(" OFFSET ");
sb.append(start);
}
return sb.toString();
}
/**
* 将RusultSet对象实例化T对象
*
* @param
* @param t
* @param rs
* @param sql
* @return t
* @throws Exception
*/
private static T instance(Class t, ResultSet rs, String sql) throws Exception{
List columns = getColumnsFromSelect(sql);
T obj = t.newInstance();
for (String col : columns) {
try{
Field f = t.getDeclaredField(col);
f.setAccessible(true);
Object v = getValue(col, f.getType().getName(), rs);
f.set(obj, v);
}catch(NoSuchFieldException e){
Field[] fields = t.getDeclaredFields();
for (Field f : fields) {
Column column = f.getAnnotation(Column.class);
if(column != null && column.name().equals(col)){
f.setAccessible(true);
Object v = getValue(col, f.getType().getName(), rs);
f.set(obj, v);
}
}
}
}
return obj;
}
private static Object getValue(String columnName, String type, ResultSet rs) throws SQLException{
Object obj = null;
// System.out.println("name="+f.getName()+", type="+f.getType().getName() );
if("java.lang.Integer".equals(type) || "int".equals(type)) {
obj = rs.getInt(columnName);
}else if("java.lang.Long".equals(type) || "long".equals(type)) {
obj = rs.getLong(columnName);
}else if("java.lang.Short".equals(type)||"short".equals(type)) {
obj = rs.getShort(columnName);
}else if("java.lang.Float".equals(type)||"float".equals(type)) {
obj = rs.getFloat(columnName);
}else if("java.lang.Double".equals(type)||"double".equals(type)) {
obj = rs.getDouble(columnName);
}else if("java.lang.Byte".equals(type)||"byte".equals(type)) {
obj = rs.getByte(columnName);
}else if("java.lang.Boolean".equals(type)||"boolean".equals(type)) {
obj = rs.getBoolean(columnName);
}else if("java.lang.String".equals(type)) {
obj = rs.getString(columnName);
}else {
obj = rs.getObject(columnName);
}
// System.out.println("name="+f.getName() +", type="+f.getType().getName()+", value="+(obj == null ? "NULL" : obj.getClass())+",{"+columnName+":"+obj+"}");
return obj;
}
/**
* 将param中的参数添加到pstate
*
* @param pstate
* @param columns
* @throws SQLException
*/
private static void setParameters(PreparedStatement pstate, Object... params) throws Exception {
if (params != null && params.length > 0) {
for (int i = 0; i < params.length; i++) {
Object value = params[i];
int j = i + 1;
if (value == null)
pstate.setString(j, "");
if (value instanceof String)
pstate.setString(j, (String) value);
else if (value instanceof Boolean)
pstate.setBoolean(j, (Boolean) value);
else if (value instanceof Date)
pstate.setDate(j, (Date) value);
else if (value instanceof Double)
pstate.setDouble(j, (Double) value);
else if (value instanceof Float)
pstate.setFloat(j, (Float) value);
else if (value instanceof Integer)
pstate.setInt(j, (Integer) value);
else if (value instanceof Long)
pstate.setLong(j, (Long) value);
else if (value instanceof Short)
pstate.setShort(j, (Short) value);
else if (value instanceof Time)
pstate.setTime(j, (Time) value);
else if (value instanceof Timestamp)
pstate.setTimestamp(j, (Timestamp) value);
else
pstate.setObject(j, value);
}
}
}
/**
* 将param中的参数添加到pstate
*
* @param pstate
* @param columns
* @param t
* @throws SQLException
*/
private static void setParameters(PreparedStatement pstate, List columns, T t) throws Exception {
if (columns != null && columns.size() > 0) {
for (int i = 0; i < columns.size(); i++) {
String attr = columns.get(i);
Object value = null;
Class c = t.getClass();
try{
Field f = c.getDeclaredField(attr);
value = f.get(t);
} catch (NoSuchFieldException e){
Field[] fields = c.getDeclaredFields();
for (Field f : fields) {
Column column = f.getAnnotation(Column.class);
if(column != null && column.name().equals(attr))
value = f.get(t);
}
}
int j = i + 1;
if (value == null)
pstate.setString(j, "");
if (value instanceof String)
pstate.setString(j, (String) value);
else if (value instanceof Boolean)
pstate.setBoolean(j, (Boolean) value);
else if (value instanceof Date)
pstate.setDate(j, (Date) value);
else if (value instanceof Double)
pstate.setDouble(j, (Double) value);
else if (value instanceof Float)
pstate.setFloat(j, (Float) value);
else if (value instanceof Integer)
pstate.setInt(j, (Integer) value);
else if (value instanceof Long)
pstate.setLong(j, (Long) value);
else if (value instanceof Short)
pstate.setShort(j, (Short) value);
else if (value instanceof Time)
pstate.setTime(j, (Time) value);
else if (value instanceof Timestamp)
pstate.setTimestamp(j, (Timestamp) value);
else
pstate.setObject(j, value);
}
}
}
/**
* 执行insert操作
*
* @param sql 预编译的sql语句
* @param t sql中的参数
* @return 执行行数
* @throws Exception
*/
public static int insert(String sql, T t) throws Exception {
Connection conn = null;
PreparedStatement pstate = null;
int updateCount = 0;
try {
conn = getConnection();
List columns = getColumnsFromInsert(sql);
pstate = conn.prepareStatement(sql);
setParameters(pstate, columns, t);
updateCount = pstate.executeUpdate();
} finally {
replease(conn, pstate, null);
}
return updateCount;
}
/**
* 执行insert操作
*
* @param sql 预编译的sql语句
* @param param 参数
* @return 执行行数
* @throws Exception
*/
public static int insert(String sql, Object... param) throws Exception {
Connection conn = null;
PreparedStatement pstate = null;
int updateCount = 0;
try {
conn = getConnection();
pstate = conn.prepareStatement(sql);
setParameters(pstate, param);
updateCount = pstate.executeUpdate();
} finally {
replease(conn, pstate, null);
}
return updateCount;
}
/**
* 执行update操作
*
* @param sql 预编译的sql语句
* @param t sql中的参数
* @return 执行行数
* @throws Exception
*/
public static int update(String sql, T t) throws Exception {
Connection conn = null;
PreparedStatement pstate = null;
int updateCount = 0;
try {
conn = getConnection();
List columns = getColumnsFromUpdate(sql);
pstate = conn.prepareStatement(sql);
setParameters(pstate, columns, t);
updateCount = pstate.executeUpdate();
} finally {
replease(conn, pstate, null);
}
return updateCount;
}
/**
* 执行update操作
*
* @param sql
* @param param 参数
* @return 执行行数
* @throws Exception
*/
public static int update(String sql, Object... param) throws Exception {
Connection conn = null;
PreparedStatement pstate = null;
int updateCount = 0;
try {
conn = getConnection();
pstate = conn.prepareStatement(sql);
setParameters(pstate, param);
updateCount = pstate.executeUpdate();
} finally {
replease(conn, pstate, null);
}
return updateCount;
}
/**
* 查询复数的对象
*
* @param t 查询结果封装的对象类型
* @param sql 预编译的sql
* @param param 查询条件
* @return List
* @throws Exception
*/
public static List queryPlural(Class t, String sql, Object... param) throws Exception {
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = getConnection();
stmt = conn.prepareStatement(sql);
setParameters(stmt, param);
rs = stmt.executeQuery();
while (rs.next()) {
list.add(instance(t, rs, sql));
}
} finally {
replease(conn, stmt, rs);
}
return list;
}
/**
* 分页查询复数的对象
*
* @param t 查询结果封装的对象类型
* @param start 开始页
* @param limit 页大小
* @param sql 预编译的sql语句
* @param param 查询参数
* @throws Exception
*/
public static List queryPluralForPagging(Class t, int start, int limit, String sql, Object... param) throws Exception {
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = getConnection();
//添加分页代码
sql = addPagingSQL(sql, start, limit);
stmt = conn.prepareStatement(sql);
setParameters(stmt, param);
rs = stmt.executeQuery();
while (rs.next()) {
list.add(instance(t, rs, sql));
}
} finally {
replease(conn, stmt, rs);
}
return list;
}
/**
* 查询单个的对象
*
* @param t 查询结果对象
* @param sql 预编译的sql
* @param param 查询参数
* @return T
* @throws Exception
*/
public static T querySingular(Class t, String sql, Object... param) throws Exception {
T obj = null;
ResultSet rs = null;
Connection conn = null;
PreparedStatement pstate = null;
try {
conn = getConnection();
pstate = conn.prepareStatement(sql);
setParameters(pstate, param);
rs = pstate.executeQuery();
if (rs.next()) {
obj = instance(t, rs, sql);
}
} finally {
replease(conn, pstate, rs);
}
return obj;
}
/**
* 查询数据量
*
* @param param 查询参数
* @param sql
* @return
* @throws SQLException
* @throws NamingException
*/
public static int queryDataCount(String sql, Object... param)
throws Exception {
int dataCount = 0;
Connection conn = null;
PreparedStatement pstate = null;
ResultSet rs = null;
try {
conn = getConnection();
sql = addCountSQL(sql);
pstate = conn.prepareStatement(sql);
setParameters(pstate, param);
rs = pstate.executeQuery();
if (rs.next()) {
dataCount = rs.getInt("dataCount");
}
} finally {
replease(conn, pstate, rs);
}
return dataCount;
}
/**
* 属性字段的注释，用于标记该属性对应的数据库字段
* 例如：
* @Column(name="user_name");
* String userName;
* 表示userName这个属性对应的数据库字段是user_name
*
* 如果属性和数据库字段完全一致，则不必标注
* @author xueliang
*/
@Target({ ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface Column{
String name() default "";
}
}