resultset

how can i close the resultSet, prepareStatement, conn in several methods below to avoid rs close and connection pool getting jammed

由 ￡可爱￡侵袭症＋ 提交于 2019-12-23 02:04:02
问题 the whole data operation is below. i want to close close each and every resource without interfering with the next connection. should i change the constructor to a connection() mthod then have a disconnect() mthod, but after doing so where should i 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

When to close the result set (Basic ODBC question)

由 回眸只為那壹抹淺笑 提交于 2019-12-23 01:52:25
问题 I am working on some small project for the local firm and the following code runs fine on my machine, but it produces errors on their server. Currently I don't have access to that server, and this is not a field that I know a lot about, so I have to ask you guys. The page is written in the classic ASP (javascript for scripting). The logic goes like this: conn.Open("myconnection"); bigQuery = "..."; rs = conn.execute(bigQuery); while (!rs.eof) { ... smallQuery = "..." rssmall = conn.execute

JavaEE基础(06)：Servlet整合C3P0数据库连接池

由 爷，独闯天下 提交于 2019-12-22 22:48:58
本文源码： GitHub·点这里 || GitEE·点这里 一、C3P0连接池 1、C3P0简介 C3P0是一个开源的JDBC连接池，应用程序根据C3P0配置来初始化数据库连接，可以自动回收空闲连接的功能。 2、核心依赖 <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>${mysql.version}</version> </dependency> <dependency> <groupId>com.mchange</groupId> <artifactId>c3p0</artifactId> <version>${c3p0.version}</version> </dependency> 3、配置文件 配置文件位置：放在 resources 目录下，这样C3P0组件会自动加载该配置。 <?xml version="1.0" encoding="UTF-8"?> <c3p0-config> <default-config> <!-- 核心参数配置 --> <property name="jdbcUrl">jdbc:mysql://localhost:3306/servlet-jdbc</property> <property name=

JavaEE基础(06)：Servlet整合C3P0数据库连接池

由 孤街浪徒 提交于 2019-12-22 21:47:59
本文源码： GitHub·点这里 || GitEE·点这里 一、C3P0连接池 1、C3P0简介 C3P0是一个开源的JDBC连接池，应用程序根据C3P0配置来初始化数据库连接，可以自动回收空闲连接的功能。 2、核心依赖 < dependency > < groupId > mysql </ groupId > < artifactId > mysql-connector-java </ artifactId > < version > ${mysql.version} </ version > </ dependency > < dependency > < groupId > com.mchange </ groupId > < artifactId > c3p0 </ artifactId > < version > ${c3p0.version} </ version > </ dependency > 3、配置文件 配置文件位置：放在 resources 目录下，这样C3P0组件会自动加载该配置。 <?xml version="1.0" encoding="UTF-8"?> < c3p0-config > < default-config > <!-- 核心参数配置 --> < property name = " jdbcUrl " > jdbc:mysql:/

ResultSet Memory

由 痞子三分冷 提交于 2019-12-22 18:29:06
问题 I have ResultSet of 100k records with each record has 5 cell 2 of them are of int data type and 3 are of Varchar (100) data type my question is how the memory is allocated to resultset for these data types when a query is executed from a java program specially to varchar data type is all the varchar(100) cells have same memory of 100 chars or it depends on the data each varchar(100) cell contains for example say I have the following record with two cell on varchar(100) -----------------------

JDBC连接MySQL/SQL注入

由 对着背影说爱祢 提交于 2019-12-22 13:02:21
一、JDBC连接MySQL： 　　1. 添加驱动：mysql-connector-java-5.1.47.jar 　　2. 创建连接： 　　（1）加载驱动：Class.forName("com.mysql.jdbc.Driver"); 　　　　//jdk1.6 以后无需再加载驱动；再引用库 META-INF下会自动加载，但是web项目还是要加载； 　　（2 ）获取连接对象： DriverManager.getConnection(url, user, password)； 　　3. 创建 SQL 语句： 　　4. 发送 sql 到数据库； 　　5. 执行 sql 语句； 　　6. 获取返回的结果： 　　　　1）DQL返回查询的结果集； 　　　　2）DML返回影响的行数； 　　　　3）DDL返回0； 　　7. 处理结果； 　　8. 释放资源： Connection.close()；Statement.close()； public class Test { public static void main(String[] args) throws Exception { // 1、加载驱动 //把com.mysql.jdbc.Driver这份字节码加载进JVM //当一份字节码被加载到JVMs时，就会执行该字节码中的静态代码块 Class.forName("com.mysql

Merging Multiple ResultSet into Single ResultSet in Java

由 我的未来我决定 提交于 2019-12-22 12:20:54
问题 Let say I have multiple ResultSet(each resultSet would refer to 1 row in database) (they are of same table.) . Now I want to create consolidated ResultSet which would intern have all other resultSet. So my primary goal is to create a combined ResultSet which would point to all rows which where previously pointed by individual resultSet. I am using Java. Do any one know how pragmatically we can achieve this? Edit : we are using java.sql.ResultSet . Edit : To make it more clear : Let say I have

Error with “TYPE_FORWARD_ONLY” in sqlite

由 烈酒焚心 提交于 2019-12-22 09:54:27
问题 I am working with SQLite and JDBC and getting this error about the result_set being TYPE_FORWARD_ONLY. PreparedStatement get_mileage = conn.prepareStatement("SELECT * FROM workout_log"); ResultSet mileage_count = get_mileage.executeQuery(); mileage_count.absolute(week_start); for (int i=week_start;i<=week_finish;i++){ total_mileage+=mileage_count.getInt(1); mileage_count.next(); } The error is on the call to absolute() even though I know it is not moving backwards at all. I have tried adding

Search a ResultSet for a specific value method?

由 a 夏天 提交于 2019-12-22 08:37:30
问题 Is there a ResultSet method that I can use that would search through a ResultSet and check whether it has the specific value/element? Similar to ArrayList.contains() method. If there isn't, you don't need to type up a search method, I'll make one :) Thanks in advance. 回答1: Don't do the search in Java side. That's unnecessarily slow and memory hogging. You're basically taking over the job the DB is designed for. Just let the DB do the job it is designed for: selecting and returning exactly the

How to process data from large ResultSet without loading them all to memory?

由 末鹿安然 提交于 2019-12-22 01:19:03
问题 My Database is hosting on mysql server & I'm using Java to analyze data. My issue: after execute 'Select' query will return a 2.5 GB result set. I don't want to load all the data to memory. So is there any ways that I could continuously retrieve data & process it? 'limit by rows' will not be an option, b/c this 2.5 GB data is joined & retrieved from 4 tables. So 'limit by rows' will increase my total run-time a lot. I've tried statement.setFetchSize(50), but it seemed not working as I
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