Tampilkan postingan dengan label JDBC. Tampilkan semua postingan
Tampilkan postingan dengan label JDBC. Tampilkan semua postingan

Rabu, 21 Desember 2016

You can convert a java.util.Date to java.sql.Timestamp value by using the getTime() method of Date class. This method return the long millisecond value from Epoch (1st January 1970 midnight) which you can pass to java.sql.Timestamp to create a new instance of Timestamp object in JDBC. Remember, java.sql.TimeStamp class is a wrapper around java.util.Date to allow JDBC to view it as SQL TIMESTAMP value. Only way to create a Timestamp instance is by passing the long time value because the second constructor of Timestamp class, which accepts individual fields e.g. year, month, date, hour, minute, second and nano is deprecated. Timestamp class can also hold up-to nano second value.
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Senin, 10 Oktober 2016

The JDBC ResultSet doesn't provide any isEmpty(), length() or size() method to check if its empty or not. Hence, when a Java programmer needs to determine if ResultSet is empty or not, it just calls the next() method and if next() return false it means ResultSet is empty. This is correct but the main problem with this approach is if the ResultSet is not empty then you may miss the first row if you follow the standard idiom to iterate over ResultSet and get the rows which involve calling next() method of ResultSet in a while loop. The key thing, which you need to remember is that initially the ResultSet's cursor points to before the first row when you call the next() method it points to the first row and if you don't get this data and calls the next() method again then you will lose the first row.
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Sabtu, 03 September 2016

The error "java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/test" occurs when you try to connect MySQL database running on your localhost, listening on port 3306 port from Java program but either you don't have MySQL JDBC driver in your classpath or driver is not registered before calling the getConnection() method. Since JDBC API is part of JDK itself, when you write a Java program to connect any database like MySQL, SQL Server or Oracle, everything compiles fine, as you only use classes from JDK but at runtime, when the JDBC driver which is required to connect to database is not available, JDBC API either throws this error or "java.lang.ClassNotFoundException: com.mysql.jdbc.Driver".
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Senin, 15 Agustus 2016

One of the tricky question from Java Interview is, "Can we pass a Timestamp instance to a method expecting java.util.Date?", it's a tricky question because the answer is both Yes and No. You can, of course, pass a Timestamp object to a method with the argument as Date because first, Timestamp is a subclass of java.util.Date and second it contains both date and time values which are missing in either java.sql.Date and java.sql.Time. So there is more reason to pass a Timestamp value to Date but you should not be doing that. Why? because Timestamp is not exactly Date. It's a composite type of java.util.Date and an additional nanosecond value which is fitted there to confirm database DATETIME data type, which supports nanosecond precision. If you look at the implementation of java.sql.Timestamp class, you will find that the long value supplied by Date is stored separately then this nanosecond value.
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Senin, 27 Juni 2016

You often need to convert java.sql.Date to java.util.Date while interacting with databases from Java application. Since JDBC the Java API for database connectivity uses java.sql.Date to represent and most of the java code accepts java.util.Date, you have no choice but to convert SQL date to util date in Java. Though, there is some fundamental difference between them e.g. java.sql.Date only contains date part e.g. day, month, and year, it doesn't contain any time attributes, but java.util.Date contains both date and time attributes e.g. hour, minutes, seconds and milliseconds. So, when you convert a java.sql.Date to java.util.Date, the resultant java.util.Date instance has the time part as zero i.e 00:00:00 to reflect midnight.
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Jumat, 18 Januari 2013

Setting JNDI Database Connection pool in Spring and Tomcat is pretty easy. Tomcat server documentation gives enough information on how to setup connection pool in Tomcat 5, 6 or 7. Here we will use Tomcat 7 along with spring framework for creating a connection pool in Tomcat server and accessing them in Spring using JNDI code. In our last article, we have seen how to setup database connection pool in Spring for core Java application which doesn't run on web server or application server and doesn't have managed J2EE container. but if you are developing web application than its better to use server managed connection pool and access them using JNDI. Spring configuration will be generic and just based on JNDI name of Datasource so it will work on any J2EE Server e.g. glassfish, WebLogic, JBoss or WebSphere until JNDI name is same. Tomcat is my favorite web server and I use it a lot on development and its comes integrated with IDE like Eclipse and Netbeans. I am using it for all test and development purpose, Though beware with java.lang.OutOfMemoryError: PermGen space in tomcat,
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Rabu, 02 Januari 2013

JDBC API in Java allows program to batch insert and update data into database, which tends to provide better performance by simple virtue of fact that it reduce lot of database round-trip which eventually improves overall performance. In fact it�s one of JDBC best practices to insert and update data in batches. For those who doesn�t know what is batch insert and update, Java provides several ways to execute SQL queries, one of them is JDBC batch insert and update, on which instead of executing sql query one by one using either Statement or PreparedSatement, you execute query in batch and send a batch of query to database for execution instead of single query. Since multiple queries are combined into batch and one batch is sent to database instead of individual queries, it reduce database round trip by factor of batch size. Batch size can be anything but needs to be decided carefully. JDBC specification supports upto 100 but individual database e.g. Oracle, MySQL, Sybase or SQL Server has there own limit on maximum batch size, , normal jdbc batch size ranges from 50 to 100. JDBC API provides addBatch() method to add queries into batch and than later execute them using executeBatch() method. Both Statement and PreparedStatement can be used to execute batch queries in Java. By the way batch insert and update also provide performance boost to Data access Object or DAO layer, as discussed in our last post 4 ways to improve Performance of JDBC applications.
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Jumat, 07 Desember 2012

JDBC Interview Question and Answer
JDBC Questions are integral part of any Java interview, I have not seen any Java Interview which is completed without asking single JDBC Interview question, there are always at least one or two question from JDBC API. Some of the popular questions like Why you should use PreparedStatement in Java, Difference between PreparedStatement and CallableStatement in Java and few questions is related to improving performance of JDBC layer by applying some JDBC performance tips. In this article I have summarized few frequently asked questions in JDBC, they ranges from easy to difficult and beginner to advanced. Questions like distributed transaction management and 2 phase commitis tough to answer until you have real experience but mostly asked in various J2EE interviews. This is not an extensive list of JDBC question answers but practicing or revising this question before going to any Java interview certainly helps.
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Minggu, 28 Oktober 2012

Difference between java.sql.Time, java.sql.Timestamp and java.sql.Date is most common JDBC question appearing on many core Java interviews. As JDBC provides three classes java.sql.Date, java.sql.Time and java.sql.Timestamp to represent date and time and you already have java.util.Date which can represent both date and time, this question poses lot of confusion among Java programmer and that�s why this is one of those tricky Java questions which is tough to answer. It becomes really tough if differences between them is not understood correctly. We have already seen some frequently asked or common JDBC questions like why JDBC has java.sql.Date despite java.util.Date and Why use PreparedStatement in Java in our last tutorials and we will see difference between java.sql.Date, java.sql.Time and java.sql.Timestamp in this article. By the way apart from these JDBC interview questions, if you are looking to get most from JDBC you can also see 4 JDBC performance tips and 10 JDBC best practices to follow. Those article not only help you to understand and use JDBC better but also help on interviews. Let�s come back to difference sql time, timestamp and sql date.
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Selasa, 28 Agustus 2012

Java JDBC Best practices
JDBC Best Practices are some coding practices which Java programmer should follow while writing JDBC code. As discussed in how to connect to Oracle database from Java, JDBC API is used to connect and interact with a Database management System. We have touched some of the JDBC best practices in our last article 4 JDBC Performance tips, On which we have discussed simple tips to improve performance of Java application with database. By using JDBC you can execute DDL, DML and Stored Procedures. JDBC Best practices is probably most significant set of coding practices in Java because it significantly affect performance of Java application. I have seen substantial performance gain by simply following common JDBC best practices like running queries with auto commit mode disable. One of the query which we used in our example of JDBC Batch update was taking almost 30 second to finish with auto commit mode enabled but it just took under one second with auto commit mode disable and using explicit commit. This JDBC tutorial is collection of such practices which help you to write better JDBC code and in most cases result in improved performance.
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