エラー
「localhost:5432 への接続が拒絶されました。ホスト名とポート番号が正しいことと、postmaster がTCP/IP接続を受け付けていることを確認してください。」
環境
- IntelliJ IDEA community版 (2020.2.4)
- WSL2(Ubuntu 20.04)
- PostgreSQL 12.7
- PostgreSQLでテーブル作成が完了していること（テーブルの中身は任意）
原因
- PostgreSQLが起動していない
- 接続するURL（ホスト名、ポート番号）が誤っている
対処法
PostgreSQLが起動しているかWSL2上で確認しましょう。
こうなっていたらPostgreSQLは起動していません。
# /etc/init.d/postgresql status
12/main (port 5432): down
rootユーザでPostgreSQLを起動させましょう。
5432番ポートで起動したことが確認できます。
# /etc/init.d/postgresql start
* Starting PostgreSQL 12 database server [ OK ]
# /etc/init.d/postgresql status
12/main (port 5432): online
IntelliJ IDEAでJavaプログラムを再実行しましょう。
参考：エラーログ
"C:\Program Files\Java\jdk-11\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2020.2.4\lib\idea_rt.jar=63885:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2020.2.4\bin" -Dfile.encoding=UTF-8 -classpath 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scratch_7
org.postgresql.util.PSQLException: localhost:5432 への接続が拒絶されました。ホスト名とポート番号が正しいことと、postmaster がTCP/IP接続を受け付けていることを確認してください。
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:285)
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:217)
at org.postgresql.Driver.makeConnection(Driver.java:458)
at org.postgresql.Driver.connect(Driver.java:260)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:677)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:228)
at scratch_7.main(scratch_7.java:29)
Caused by: java.net.ConnectException: Connection refused: connect
at java.base/java.net.PlainSocketImpl.waitForConnect(Native Method)
at java.base/java.net.PlainSocketImpl.socketConnect(PlainSocketImpl.java:107)
at java.base/java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:399)
at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:242)
at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:224)
at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:403)
at java.base/java.net.Socket.connect(Socket.java:591)
at org.postgresql.core.PGStream.<init>(PGStream.java:81)
at org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:93)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:197)
... 7 more
プロセスは終了コード 0 で完了しました