postgresql数据库-Java连接PostgreSQL数据库

跨零代码为大家提供高品质的解决方案,请大家多多来访,跨零不胜感激,在此谢过。

在Java程序中使用PostgreSQL之前,我们需要确保在机器上安装了PostgreSQL JDBC和Java。 您可以在机器上检查是否正确安装了Java:Java教程。 现在我们来看一下如何设置PostgreSQL JDBC驱动。

  • postgresql-jdbc存储库下载最新版本的postgresql-(VERSION).jdbc.jar

  • 在类路径中添加下载的jar文件postgresql-(VERSION).jdbc.jar,或者您可以使用-classpath选项,如下面的例子所述。

Java连接到PostgreSQL数据库

以下Java代码显示如何连接到现有数据库。 如果数据库不存在,那么它将被创建,最后将返回一个数据库对象。

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");    } } 

在编译并运行上述程序之前,请在PostgreSQL安装目录中找到pg_hba.conf文件并添加以下行:

# IPv4 local connections: host    all         all         127.0.0.1/32          md5 

您可以启动/重新启动postgres服务器,使用以下命令运行:

[root@host]# service postgresql restart Stopping postgresql service:                               [  OK  ] Starting postgresql service:                               [  OK  ] 

现在,我们来编译并运行上面的程序来获得与testdb的连接。 在这里使用用户ID为postgres和密码为123来访问数据库。 您可以根据数据库配置和设置进行更改。 我们还假定当前版本的JDBC驱动程序postgresql-9.2-1002.jdbc3.jar在当前路径中(c:/tools/)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 

创建表

以下Java程序将用于在之前打开的数据库中创建一个表。确保目标数据库中没有此表。

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");      } } 

编译和执行程序时,将在testdb数据库中创建COMPANY表,并显示以下两行:

Opened database successfully Table created successfully 

插入数据操作

以下Java程序显示了如何在上述示例中创建的COMPANY表中创建/插入数据记录:

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");    } } 

程序编译执行后,将在COMPANY表中创建/插入给定的记录,并显示以下两行:

Opened database successfully Records created successfully 

SELECT操作

以下Java程序显示了如何从上述示例中创建的COMPANY表中获取和显示记录:

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");      } } 

程序编译执行时,会产生以下结果:

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 

更新操作

以下Java代码显示了如何使用UPDATE语句来更新指定记录,然后从COMPANY表中获取和显示更新的记录:

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");      } } 

程序编译执行时,会产生以下结果:

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 

删除操作

以下Java代码显示了如何使用DELETE语句删除指定记录,然后从COMPANY表中获取并显示剩余的记录:

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");      } } 

程序编译执行时,会产生以下结果:

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 

  

上一篇: C/C++连接PostgreSQL数据库 下一篇: PHP连接PostgreSQL数据库

加QQ群啦,易百教程官方技术学习群

从零到一,创造未来!跨零综合IT问题解决服务站,欢迎你的到来。Oracle数据库教程 postgresql数据库/a> 只为你绽放。

本文固定链接: http://kua0.com/2019/11/12/postgresql数据库-java连接postgresql数据库/

为您推荐

发表评论

电子邮件地址不会被公开。 必填项已用*标注