- JDBC A specification of the Java language to access a database is a set of APIs. The JDBC (Java database Connectivity) API, the Java Databases programming interface, is a standard set of interfaces and classes in the Java language that can be used by Java client programs to access a variety of different types of databases. such as the establishment of database connections, execute SQL statements for data access operations. Register driver operation: The standard way to establish a connection to a database is to call the Drivermanager.getconnection method. The method accepts a string that contains a URL. The DriverManager class, known as the JDBC Management layer, will attempt to find a driver that can connect to the database that the URL represents. The DriverManager class contains a list of registered driver classes. When the method getconnection is called, it checks each driver in the manifest until it finds a driver that can connect to the database specified in the URL. Driver method Connect uses this URL to establish an actual connection. Get connection Action object: To get an operand can be obtained by DriverManager's getconnection (). Close the Connection action object: Use Close () to close the connection to the database, or you can use the attempt to automatically turn off resource syntax to simplify program composition.
- Statement Statement's ExecuteQuery () method is the Sql,executeupdate () that is used for querying a database such as SELECT, which returns an int result representing the number of changes in the data, ExecuteQuery () Returns a Java.sql.ResultSet object that represents the result of the query, and the result of the query is a sum of data. You can use ResultSet's next () to move to the next data, which returns TRUE or false to indicate whether there is a next piece of data, and then you can use GETXXX () to get the data. If some of the actions are just some of the parameters in the SQL statement that are different, the rest of the SQL clauses are the same, you can use Java.sql.PreparedStatement. You can use the connection PreparedStatement () method to create good one precompiled (precompile) SQL commands, where the parameters change, specifying "?" first. The placeholder character. When you need to really specify the parameters to execute, then use the corresponding Setint (), setString () and other methods, specify "?" The parameters that should be true.
- reflection and Class loader Java actually requires a class to load the corresponding. class document, rather than loading all classes at program startup. An instance of Java.lang.Class represents a. class document that is loaded when the Java application runs. The class object corresponding to each object can be obtained through the GetClass () method of object, or through a. Class constant, and if it is a base type, the class object can also be obtained by using the corresponding package classes plus. Type. For example: Integer.type can get a class object representing int. If you do not know the class name beforehand, you can use Class.forName () to dynamically load the. class document, and then use its newinstance () method to build the class instance after the class object is obtained. The Java.lang.reflect.Method instance is the representative object of the method, and you can use the Invoke () method to invoke the specified method dynamically.
20145301 Java programming Nineth Week of study summary
