如何在以下几种方法中关闭 resultSet、prepareStatement、conn 以避免 rs 关闭和连接池被卡住
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【中文标题】如何在以下几种方法中关闭 resultSet、prepareStatement、conn 以避免 rs 关闭和连接池被卡住【英文标题】：how can i close the resultSet, prepareStatement, conn in several methods below to avoid rs close and connection pool getting jammed 【发布时间】：2012-01-27 14:01:54 【问题描述】：整个数据操作如下。我想在不干扰下一个连接的情况下关闭每个资源。我应该将构造函数更改为 connection() 方法然后有一个 disconnect() 方法，但是这样做之后我应该在哪里
public class DataBean
private Connection conn = null;
private ResultSet res = null;
private InitialContext context;
private DataSource datasource;
private Statement stmt=null;
private java.sql.PreparedStatement prepar = null;
private java.sql.CallableStatement proc = null;
public static int PAGECOUNT; //²éѯºó·µ»ØµÄ×ÜÒ³Êý ÒòΪjavaµÄº¯Êý²»ÄÜ´«ÒýÓÃËùÒÔÐèÒªÓþ²Ì¬±äÁ¿À´»ñµÃ
public DataBean()
try
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/MyData", "root","loikenu");
context = new InitialContext();
datasource = (DataSource)context.lookup("jdbc/MyData");
conn = datasource.getConnection();
//stmt =conn.createStatement();
catch (Exception e)
JOptionPane.showMessageDialog(null, e.getMessage());
public UserBean checkUsersLogin(String userName, String userPwd) //µÇ½ÑéÖ¤
UserBean ub = null;
if (!checkParameter(userName + userPwd))
userName = "null";
userPwd = "null";
try
String sql =
"select count(*) from admin where userName=? and userPwd=?";
prepar = conn.prepareStatement(sql);
//set parameter values for preparedstatment object
prepar.setString(1, userName);
prepar.setString(2, userPwd);
//execute query using preparedstatement object
res = prepar.executeQuery();
if (res.next())
//get data from reults set returned by jdbc
if (res.getInt(1) > 0)
ub = this.getUser(userName);
else
ub = null;
catch (Exception e)
ub = null;
e.printStackTrace();
return ub;
public UserBean getUser(String userName) //ÌáÈ¡µÇ½Óû§ÐÅÏ¢
UserBean ub = new UserBean();
int i=1;
String sql = "select * from admin where userName=?";
try
prepar = conn.prepareStatement(sql);
prepar.setString(1, userName);
res = prepar.executeQuery();
while (res.next())
ub.setUserName(res.getString("userName"));
ub.setUserPwd(res.getString("userPwd"));
ub.setUserId(i);
i++;
catch (SQLException ex)
ex.printStackTrace();
return ub;
public boolean checkParameter(String para) //¹ýÂË·Ç·¨×Ö·û
int flag = 0;
flag += para.indexOf("'") + 1;
flag += para.indexOf(";") + 1;
flag += para.indexOf("1=1") + 1;
flag += para.indexOf("|") + 1;
flag += para.indexOf("<") + 1;
flag += para.indexOf(">") + 1;
if (flag != 0)
System.out.println("Ìá½»ÁË·Ç·¨×Ö·û!!!");
return false;
return true;
public ArrayList selectCDBean(String selectValue, int page, int count) //²éѯ·ÖÒ³
ArrayList list = new ArrayList();
if (!checkParameter(selectValue))
selectValue = "";
try
proc = conn.prepareCall("call proc_page(?,?,?,?)");
proc.setInt(1, page);
proc.setInt(2, count);
proc.setString(3, selectValue);
proc.registerOutParameter(4, Types.INTEGER); //OUTPUT²ÎÊý ·µ»Ø½á¹¹¹²¶àÉÙÒ³
res = proc.executeQuery(); //½ÓÊÕ´æ´¢¹ý³ÌµÄ½á¹û¼¯
while (res.next()) //ÌáÈ¡½á¹û¼¯µÄÿÌõ¼Ç¼
CDBean cb = new CDBean();
cb.setCdAlbum(res.getString("CDalbum"));
cb.setCdCompany(res.getString("CDcompany"));
cb.setCdName(res.getString("CDname"));
cb.setCdId(res.getLong("CDid"));
cb.setCdType(getCDType(res.getInt("CDtypeId")));
list.add(cb);
PAGECOUNT = proc.getInt(4);
catch (SQLException ex)
ex.printStackTrace();
return list;
public String getCDType(int cdtypeId)
ResultSet res1=null;
try
java.sql.PreparedStatement prepar1 = conn.prepareStatement(
"select display from CDtype where CDtypeId=?");
prepar1.setLong(1, cdtypeId);
res1 = prepar1.executeQuery();
res1.next();
return res1.getString("display");
catch (SQLException ex)
return null;
public boolean setCDBean(CDBean cb)
if (!checkParameter(cb.getCdName() + cb.getCdCompany() + cb.getCdAlbum() +
cb.getCdType()))
return false;
boolean flag = false;
String sql =
"update CDinfo set CDname=?,CDcompany=?,CDalbum=?,CDtypeId=? where CDid=?";
try
prepar = conn.prepareStatement(sql);
prepar.setString(1, cb.getCdName());
prepar.setString(2, cb.getCdCompany());
prepar.setString(3, cb.getCdAlbum());
prepar.setInt(4, Integer.parseInt(cb.getCdType()));
// prepar.setLong(5, cb.getCdId());
int result = prepar.executeUpdate();
if (result > 0)
flag = true;
else
flag = false;
catch (Exception ex)
flag = false;
ex.printStackTrace();
return flag;
public CDBean getCDBean(long id)
CDBean cb = new CDBean();
int i=1;
String sql = "select * from CDinfo where CDid=?";
try
prepar = conn.prepareStatement(sql);
prepar.setLong(1, id);
res = prepar.executeQuery();
while (res.next())
cb.setCdAlbum(res.getString("CDalbum"));
cb.setCdCompany(res.getString("CDcompany"));
cb.setCdName(res.getString("CDname"));
cb.setCdId(i);
cb.setCdType(getCDType(res.getInt("CDtypeId")));
i++;
catch (SQLException ex)
ex.printStackTrace();
return cb;
public boolean deleteCDBean(long id)
boolean flag = false;
String sql = "delete from CDinfo where CDid=?";
try
prepar = conn.prepareStatement(sql);
prepar.setLong(1, id);
int result = prepar.executeUpdate();
if (result > 0)
flag = true;
else
flag = false;
catch (Exception ex)
flag = false;
ex.printStackTrace();
return flag;
public boolean addCDBean(CDBean cb)
boolean flag = false;
if (!checkParameter(cb.getCdName() + cb.getCdCompany() + cb.getCdAlbum() + cb.getCdId()+
cb.getCdType()))
return false;
String sql = "insert into CDinfo values(?,?,?,default,?)";
try
this.prepar = conn.prepareStatement(sql);
prepar.setString(1, cb.getCdName());
prepar.setString(2, cb.getCdCompany());
prepar.setString(3, cb.getCdAlbum());
prepar.setInt(4, Integer.parseInt(cb.getCdType()));
int result = prepar.executeUpdate();
if (result > 0)
flag = true;
else
flag = false;
catch (Exception ex)
flag = false;
ex.printStackTrace();
return flag;
public boolean setUserBean(UserBean ub)
boolean flag = false;
String sql = "update admin set userPwd=? where userId=?";
try
if (!checkParameter(ub.getUserPwd()))
return false;
this.prepar = conn.prepareStatement(sql);
prepar.setString(1, ub.getUserPwd());
prepar.setLong(2, ub.getUserId());
int result = prepar.executeUpdate();
if (result > 0)
flag = true;
else
flag = false;
catch (Exception ex)
flag = false;
ex.printStackTrace();
return flag;
public boolean addUserBean(UserBean ub)
boolean flag = false;
String sql = "insert into admin(userName,userPwd) values(?,?)";
//int i=1;
if (!checkParameter(ub.getUserPwd() + ub.getUserName()+ub.getUserId()))
return false;
if (hasUser(ub.getUserName()))
return false;
try
prepar = conn.prepareStatement(sql,prepar.RETURN_GENERATED_KEYS);
prepar.setString(1, ub.getUserName());
prepar.setString(2, ub.getUserPwd());
// prepar.setLong(3,ub.getUserId());
int result = prepar.executeUpdate();
if (result > 0)
flag = true;
else
flag = false;
// i++;
catch (Exception ex)
flag = false;
ex.printStackTrace();
return flag;
public boolean hasUser(String userName)
boolean flag = true;
String sql = "select count(*) from admin where userName=?";
try
prepar = conn.prepareStatement(sql);
prepar.setString(1, userName);
res = prepar.executeQuery();
res.next();
int result = res.getInt(1);
if (result > 0)
flag = true;
else
flag = false;
catch (SQLException ex)
ex.printStackTrace();
flag = true;
return flag;
【问题讨论】：
【参考方案1】：public class DataBean
private Connection conn = null;
private ResultSet res = null;
// ...
private Statement stmt=null;
private java.sql.PreparedStatement prepar = null;
private java.sql.CallableStatement proc = null;
// ...
这是错误的。您不应该在类级别声明它们。您应该在方法级别声明它们。以你的getUser() 方法为例，它必须是这样的：
public UserBean getUser(String userName)
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
// ...
然后，您需要确保以相反的顺序关闭 finally 块中的资源，因为您在同一个 try 块中获取它们。这是根据推荐的 JDBC 习惯用法对 getUser() 方法的完整重写：
public UserBean getUser(String userName) throws SQLException
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
UserBean userBean = null;
String sql = "select userId, userName, userPwd from admin where userName = ?";
try
connection = dataSource.getConnection();
statement = connection.prepareStatement(sql);
statement.setString(1, userName);
resultSet = statement.executeQuery();
if (resultSet.next())
userBean = new UserBean();
userBean.setUserId(resultSet.getInt("userId");
userBean.setUserName(resultSet.getString("userName"));
userBean.setUserPwd(resultSet.getString("userPwd"));
finally
if (resultSet != null) try resultSet.close(); catch (SQLException logOrIgnore)
if (statement != null) try statement.close(); catch (SQLException logOrIgnore)
if (connection != null) try connection.close(); catch (SQLException logOrIgnore)
return userBean;
（请注意，我将用户 ID 固定为数据库列字段，使其成为自动增量 PK，还请注意，我将 while 固定为 if - 只有 1 个用户这个名字，对吧？-，还要注意它返回null，当没有已知用户时可以方便地检查）
另见：
How often should Connection, Statement and ResultSet be closed in JDBC? JDBC MySql connection pooling practices to avoid exhausted connection pool Am I Using JDBC Connection Pooling?您的 checkUsersLogin() 和 checkParameter() 方法也很可疑，但这是另一个问题的主题。
【讨论】：
不客气。由于您是新来的，请不要忘记标记已接受的答案，这有助于（最）解决您的问题。另见meta.stackexchange.com/questions/5234/…【参考方案2】：您必须使用相反的顺序关闭每个可关闭对象。 如果开单： 连接 PreparedStatement 结果集
那么关闭订单将是： 结果集 PreparedStatement 连接
您可以将其放入 finally 块中。这是一般规则。
【讨论】：
感谢@e-zinc，所以我应该在上面的每个方法中添加 finally 这些对象在所有情况下都必须关闭，包括异常，使用 finally 块很容易做到，当然你必须在之前检查它们是否为空。【参考方案3】：您应该使用 Java 7 try-with-resources。是的，当你问这个问题时它已经出来了！ ;)
类似的东西：
try (Connection con = // get connection... ;
PreparedStatement ps = // create prepared statement... ;
ResultSet rs = ps.executeQuery())
// Process the result set...
// The AutoCloseable resources 'conn', 'ps', and 'rs' will be cleaned up at the end:
// .close() will be called on all of them whether an exception occurs or not
catch (SQLException e)
// TODO(mykey): Do not swallow me!!
注意：请参阅AutoCloseable .close() 的文档
【讨论】：
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