在我們的 Java 程序中開始使用 PostgreSQL 之前，我們需要確保在機(jī)器上設(shè)置了 PostgreSQL JDBC 和 Java。您可以查看 Java 教程，了解如何在您的機(jī)器上安裝 Java?，F(xiàn)在讓我們檢查一下如何設(shè)置 postgresqljdbc 驅(qū)動(dòng)程序。
從后面地址下載最新版本的postgresql-(version).jdbc.jar postgresql-jdbc 下載.
添加下載的 jar 文件 postgresql-(VERSION).jar，或者您可以將其與-classpath 選項(xiàng)一起使用，如下面的示例所示。
下面的部分假設(shè)您對(duì) javajdbc 概念有所了解。如果沒有，那么建議您花半個(gè)小時(shí)學(xué)習(xí) JDBC 教程，以熟悉下面解釋的概念。
下面的Java代碼展示了如何連接到現(xiàn)有數(shù)據(jù)庫。如果數(shù)據(jù)庫不存在，那么將創(chuàng)建它，最后將返回一個(gè)數(shù)據(jù)庫對(duì)象。
import java.sql.Connection;
import java.sql.DriverManager;
public class PostgreSQLJDBC {
public static void main(String args[]) {
Connection c = null;
try {
Class.forName("org.postgresql.Driver");
c = DriverManager
.getConnection("jdbc:postgresql://localhost:5432/testdb",
"postgres", "123");
} catch (Exception e) {
e.printStackTrace();
System.err.println(e.getClass().getName()+": "+e.getMessage());
System.exit(0);
}
System.out.println("Opened database successfully");
}
}在編譯和運(yùn)行上述程序之前，請(qǐng)找到pg_hba.conf文件在PostgreSQL安裝目錄中創(chuàng)建一個(gè)文件，并添加以下行:
# IPv4 local connections: host all all 127.0.0.1/32 md5
如果postgres服務(wù)器沒有運(yùn)行，可以使用以下命令啟動(dòng)/重新啟動(dòng)postgres服務(wù)器：
現(xiàn)在，讓我們編譯并運(yùn)行上面的程序來連接testdb。這里，我們使用postgres作為用戶ID, 123作為密碼來訪問數(shù)據(jù)庫。您可以根據(jù)數(shù)據(jù)庫配置和設(shè)置進(jìn)行更改。我們還假設(shè)當(dāng)前版本的JDBC驅(qū)動(dòng)程序postgresql-9.2-1002.jdbc3.jar在當(dāng)前路徑中可用。
C:\JavaPostgresIntegration>javac PostgreSQLJDBC.java C:\JavaPostgresIntegration>java -cp c:\tools\postgresql-9.2-1002.jdbc3.jar;C:\JavaPostgresIntegration PostgreSQLJDBC Open database successfully
下面的 Java 程序?qū)⒂糜谠谝郧按蜷_的數(shù)據(jù)庫中創(chuàng)建一個(gè)表。請(qǐng)確保目標(biāo)數(shù)據(jù)庫中沒有此表。
import java.sql.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
public class PostgreSQLJDBC {
public static void main( String args[] ) {
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.postgresql.Driver");
c = DriverManager
.getConnection("jdbc:postgresql://localhost:5432/testdb",
"manisha", "123");
System.out.println("Opened database successfully");
stmt = c.createStatement();
String sql = "CREATE TABLE COMPANY " +
"(ID INT PRIMARY KEY NOT NULL," +
" NAME TEXT NOT NULL, " +
" AGE INT NOT NULL, " +
" ADDRESS CHAR(50), " +
" SALARY REAL)";
stmt.executeUpdate(sql);
stmt.close();
c.close();
} catch ( Exception e ) {
System.err.println( e.getClass().getName()+": "+ e.getMessage() );
System.exit(0);
}
System.out.println("Table created successfully");
}
}編譯和執(zhí)行程序時(shí)，它將在testdb數(shù)據(jù)庫中創(chuàng)建COMPANY表，并顯示以下兩行-
Opened database successfully Table created successfully
下面的Java程序顯示了如何在上面示例中創(chuàng)建的COMPANY表中創(chuàng)建記錄-
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
public class PostgreSQLJDBC {
public static void main(String args[]) {
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.postgresql.Driver");
c = DriverManager
.getConnection("jdbc:postgresql://localhost:5432/testdb",
"manisha", "123");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
String sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) "
+ "VALUES (1, 'Paul', 32, 'California', 20000.00 );";
stmt.executeUpdate(sql);
sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) "
+ "VALUES (2, 'Allen', 25, 'Texas', 15000.00 );";
stmt.executeUpdate(sql);
sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) "
+ "VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );";
stmt.executeUpdate(sql);
sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) "
+ "VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );";
stmt.executeUpdate(sql);
stmt.close();
c.commit();
c.close();
} catch (Exception e) {
System.err.println( e.getClass().getName()+": "+ e.getMessage() );
System.exit(0);
}
System.out.println("Records created successfully");
}
}在編譯和執(zhí)行上述程序時(shí)，它將在 COMPANY 表中創(chuàng)建給定的記錄，并顯示以下兩行-
Opened database successfully Records created successfully
下面的Java程序展示了我們?nèi)绾螐纳厦媸纠袆?chuàng)建的COMPANY表中獲取和顯示記錄
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class PostgreSQLJDBC {
public static void main( String args[] ) {
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.postgresql.Driver");
c = DriverManager
.getConnection("jdbc:postgresql://localhost:5432/testdb",
"manisha", "123");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" );
while ( rs.next() ) {
int id = rs.getInt("id");
String name = rs.getString("name");
int age = rs.getInt("age");
String address = rs.getString("address");
float salary = rs.getFloat("salary");
System.out.println( "ID = " + id );
System.out.println( "NAME = " + name );
System.out.println( "AGE = " + age );
System.out.println( "ADDRESS = " + address );
System.out.println( "SALARY = " + salary );
System.out.println();
}
rs.close();
stmt.close();
c.close();
} catch ( Exception e ) {
System.err.println( e.getClass().getName()+": "+ e.getMessage() );
System.exit(0);
}
System.out.println("Operation done successfully");
}
}當(dāng)程序被編譯和執(zhí)行時(shí)，會(huì)產(chǎn)生以下結(jié)果
Opened database successfully ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 20000.0 ID = 2 NAME = Allen AGE = 25 ADDRESS = Texas SALARY = 15000.0 ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0 ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0 Operation done successfully
下面的Java代碼展示了如何使用UPDATE語句更新任何記錄，然后從我們的COMPANY表中獲取并顯示更新后的記錄
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class PostgreSQLJDBC {
public static void main( String args[] ) {
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.postgresql.Driver");
c = DriverManager
.getConnection("jdbc:postgresql://localhost:5432/testdb",
"manisha", "123");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
String sql = "UPDATE COMPANY set SALARY = 25000.00 where ID=1;";
stmt.executeUpdate(sql);
c.commit();
ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" );
while ( rs.next() ) {
int id = rs.getInt("id");
String name = rs.getString("name");
int age = rs.getInt("age");
String address = rs.getString("address");
float salary = rs.getFloat("salary");
System.out.println( "ID = " + id );
System.out.println( "NAME = " + name );
System.out.println( "AGE = " + age );
System.out.println( "ADDRESS = " + address );
System.out.println( "SALARY = " + salary );
System.out.println();
}
rs.close();
stmt.close();
c.close();
} catch ( Exception e ) {
System.err.println( e.getClass().getName()+": "+ e.getMessage() );
System.exit(0);
}
System.out.println("Operation done successfully");
}
}當(dāng)程序被編譯和執(zhí)行時(shí)，會(huì)產(chǎn)生以下結(jié)果
Opened database successfully ID = 2 NAME = Allen AGE = 25 ADDRESS = Texas SALARY = 15000.0 ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0 ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0 ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 25000.0 Operation done successfully
下面的Java代碼展示了如何使用DELETE語句刪除任何記錄，然后從我們的COMPANY表中獲取并顯示剩余的記錄
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class PostgreSQLJDBC6 {
public static void main( String args[] ) {
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.postgresql.Driver");
c = DriverManager
.getConnection("jdbc:postgresql://localhost:5432/testdb",
"manisha", "123");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
String sql = "DELETE from COMPANY where ID = 2;";
stmt.executeUpdate(sql);
c.commit();
ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" );
while ( rs.next() ) {
int id = rs.getInt("id");
String name = rs.getString("name");
int age = rs.getInt("age");
String address = rs.getString("address");
float salary = rs.getFloat("salary");
System.out.println( "ID = " + id );
System.out.println( "NAME = " + name );
System.out.println( "AGE = " + age );
System.out.println( "ADDRESS = " + address );
System.out.println( "SALARY = " + salary );
System.out.println();
}
rs.close();
stmt.close();
c.close();
} catch ( Exception e ) {
System.err.println( e.getClass().getName()+": "+ e.getMessage() );
System.exit(0);
}
System.out.println("Operation done successfully");
}
}當(dāng)程序被編譯和執(zhí)行時(shí)，會(huì)產(chǎn)生以下結(jié)果
Opened database successfully ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0 ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0 ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 25000.0 Operation done successfully