java过程语言插件-pl/java在postgresql9.6中的安装及使用

pl/java简介

pl/java是一个postgreSQL数据库插件，与pl/sql、pl/perl、pl/python类似，安装该插件之后，函数和触发器可以用java语言实现然后加载进数据库。pljava开发工作于2003年开始，2005年1月第一个正式版本发布。

pl/java下载

git clone https://github.com/tada/pljava

pl/java构建条件

1、C程序编译链接工具，gcc g++ (笔者版本为4.8.5，推荐4.3.0以上版本)
2、jdk（笔者版本为openjdk1.8，1.7以下版本可能会某些依赖下载失败）
3、安装postgre数据库，pg_config路径加入环境变量
4、pljava由maven构建，需要安装maven(不低于3.0.4版本)
note：建议不要用yum安装maven, yum安装的maven版本一般比较低，编译过程可能会由于依赖库版本问题导致编译失败，建议手动下载maven 3.6以上的版本

Building pl/java

1、下载pl/java源码到指定目录

[qin@pcmk2 pljava-master]$ pwd
/home/qin/pljava-master

2、进入源码根目录执行命令：mvn clean install

[qin@pcmk2 pljava-master]$ ls
COPYRIGHT  docs  freenode.ver  pljava  pljava-ant  pljava-api  pljava-examples  pljava-packaging  pljava-so  pom.xml  README.md  src  target
[qin@pcmk2 pljava-master]$ mvn clean install

note: 第一次构建，有很多依赖库需要下载，构建过程可能会需要几个小时，请耐心等待，二次构建就会变快

3、构建成功后显示如下：

```bash
[INFO] Executed tasks
[INFO] 
[INFO] --- maven-install-plugin:2.5.2:install (default-install) @ pljava-packaging ---
[INFO] Installing /home/qin/pljava-master/pljava-packaging/pom.xml to /home/qin/.m2/repository/org/postgresql/pljava-packaging/1.6.0-SNAPSHOT/pljava-packaging-1.6.0-SNAPSHOT.pom
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for PostgreSQL PL/Java 1.6.0-SNAPSHOT:
[INFO] 
[INFO] PostgreSQL PL/Java ................................. SUCCESS [  2.224 s]
[INFO] PL/Java API ........................................ SUCCESS [ 14.573 s]
[INFO] PL/Java backend Java code .......................... SUCCESS [  5.684 s]
[INFO] PL/Java backend native code ........................ SUCCESS [ 22.446 s]
[INFO] PL/Java Ant tasks .................................. SUCCESS [  0.587 s]
[INFO] PL/Java examples ................................... SUCCESS [12:23 min]
[INFO] PL/Java packaging .................................. SUCCESS [15:00 min]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  28:11 min
[INFO] Finished at: 2020-05-02T18:48:34+08:00
[INFO] ------------------------------------------------------------------------

构建成功之后pljava-packaging/target子目录下的jar文件pljava-pg9.6-amd64-Linux-gpp.jar，包含有安装pljava所需的所有文件，java -jar命令可以把jar包所包含的文件提取出来并自动放入postgresql安装目录extension子目录下。

安装pl/java进入postgreSQL 9.6

1、build完成之后，执行以下命令，可以安装Pl/java extension进入postgresql安装目录
cd ~/pljava-master/pljava-packaging/target
java -jar pljava-pg9.6-amd64-Linux-gpp.jar

[qin@pcmk2 target]$ java -jar pljava-pg9.6-amd64-Linux-gpp.jar 
/home/qin/pg96/lib/postgresql/libpljava-so-1.6.0-SNAPSHOT.so as bytes
/home/qin/pg96/share/postgresql/pljava/pljava-1.6.0-SNAPSHOT.jar as bytes
/home/qin/pg96/share/postgresql/pljava/pljava-api-1.6.0-SNAPSHOT.jar as bytes
/home/qin/pg96/share/postgresql/pljava/pljava-examples-1.6.0-SNAPSHOT.jar as bytes
/home/qin/pg96/share/postgresql/extension/pljava.control as lines (ASCII)
/home/qin/pg96/share/postgresql/pljava/pljava--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--unpackaged--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.5--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.4--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.3--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.2--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.1--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.1-BETA3--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.1-BETA2--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.1-BETA1--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.0--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.0-BETA3--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.0-BETA2--1.6.0-SNAPSHOT.sql as lines (UTF8)
/home/qin/pg96/share/postgresql/pljava/pljava--1.5.0-BETA1--1.6.0-SNAPSHOT.sql as lines (UTF8)
[qin@pcmk2 target]$ pwd
/home/qin/pljava-master/pljava-packaging/target

2、执行完成后，进入postgresql安装目录下extension子目录，可以发现pljava库文件已经生成

3、在create extension之前还必须设置一个数据库环境变量pljava.libjvm_location，该变量告诉pljava使用的java库文件位置
可以在postgresql.conf中填加：
pljava.libjvm_location=’/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64/jre/lib/amd64/server/libjvm.so’
该环境变量为会话级，也可以：
SET pljava.libjvm_location TO ‘/usr/lib/jvm/java-1.8.0/lib/…’;

4、psql登录数据库执行create exteinsion：

postgres=# CREATE EXTENSION pljava;
CREATE EXTENSION

5、插件创建成功

postgres=# \dL
                                                      List of languages
  Name   |  Owner   | Trusted |                                         Description                                          
---------+----------+---------+----------------------------------------------------------------------------------------------
 java    | postgres | t       | Trusted/sandboxed language for routines and types in Java; http://tada.github.io/pljava/
 javau   | postgres | f       | Untrusted/unsandboxed language for routines and types in Java; http://tada.github.io/pljava/
 plpgsql | postgres | t       | PL/pgSQL procedural language
(3 rows)

测试plsql调用java程序

1、测试java程序Hello.java

package com.example.proj;

public class Hello {

  public static String hello(String toWhom) {
    return "Hello, " + toWhom + "!";
  }

}

2、编写manifest.txt

Manifest-Version: 1.0
Main-Class: Hello
Specification-Title: "Hello"
Specification-Version: "1.0"
Created-By: 1.8.0_252
Build-Date: 05/02/2020 21:00

3、执行如下命令，将程序编译打包

[qin@pcmk2 plj_test]$ javac -d . Hello.java
[qin@pcmk2 plj_test]$ jar cfm Hello.jar manifest.txt com 
[qin@pcmk2 plj_test]$ ls
com  Hello.jar  Hello.java  manifest.txt

4、加载包含测试程序的Jar包至数据库
pljava扩展安装之后，sqlj模式下有install_jar、replace_jar、remove_jar三个函数用于加载、替换、移除jar包到数据库中
sqlj.replace_jar(, , )函数包函三个参数
jar_url ：jar文件的URL.
jar_name：数据库中映射jar包的逻辑名.
redeploy：True if the jar should be undeployed according to the deployment descriptor of the old jar and deployed according to the deployment descriptor of the new jar, false otherwise
例：

postgres=# select sqlj.install_jar('file:///home/qin/plj_test/Hello.jar','examples', true);
 install_jar 
-------------
 
(1 row)

5、映射逻辑名examples到public模式

postgres=# SELECT sqlj.set_classpath('public', 'examples');
 set_classpath 
---------------
 
(1 row)

6、查询映射是否成功

postgres=# select sqlj.get_classpath('public');
 get_classpath 
---------------
 examples
(1 row)

7、创建plsql函数

postgres=# create or replace function say_hello(varchar) returns varchar 
postgres-# as 'com.example.proj.Hello.hello' language java;
CREATE FUNCTION
postgres=# \df
                           List of functions
 Schema |    Name    | Result data type  | Argument data types |  Type  
--------+------------+-------------------+---------------------+--------
 public | getsysprop | character varying | character varying   | normal
 public | say_hello  | character varying | character varying   | normal
(2 rows)

8、测试plsql函数功能

postgres=# select say_hello('Lining');
   say_hello    
----------------
 Hello, Lining!
(1 row)

postgres=#

参考文献：

1、https://tada.github.io/pljava/build/build.html. pl/java build指南
2、https://github.com/tada/pljava/releases. pl/java源码地址