Java实现将MarkDown保留文档内容及格式输出到浏览器页面

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已于 2025-04-19 17:56:39 修改

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分类专栏： SpringBoot 关系型数据库 java高级文章标签： java 开发语言 postgresql

于 2025-04-19 17:53:31 首次发布

本文链接：https://blog.youkuaiyun.com/m0_63615119/article/details/147353489

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项目目录

pom依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>PostgreSQL-easy</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <version>2.2.2.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.2.2.RELEASE</version>
        </dependency>

        <!-- JSON处理工具 -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>

        <!-- PostgreSQL JDBC Driver -->
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>42.2.24</version>
        </dependency>
        
        <!--  使用 CommonMark 转换 Markdown 到 HTML  -->
        <dependency>
            <groupId>org.commonmark</groupId>
            <artifactId>commonmark</artifactId>
            <version>0.21.0</version>
        </dependency>
    </dependencies>

</project>

config配置

MarkdownToHtmlConverter

使用 CommonMark 转换 Markdown 到 HTML。

package org.example.config;

import org.commonmark.parser.Parser;
import org.commonmark.renderer.html.HtmlRenderer;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MarkdownToHtmlConverter {

    public static String convert(String markdown) {
        // 创建一个 Markdown 解析器
        Parser parser = Parser.builder().build();
        // 解析 Markdown 文本
        org.commonmark.node.Node document = parser.parse(markdown);
        // 渲染为 HTML
        HtmlRenderer renderer = HtmlRenderer.builder().build();
        return renderer.render(document);
    }

    public static void main(String[] args) {
        String markdown = "# Example Function\n" +
                          "```sql\n" +
                          "CREATE FUNCTION example() RETURNS void AS $$ BEGIN END; $$;\n" +
                          "```";
        String html = convert(markdown);
        System.out.println(html);
    }
}

PostgreSQLStaticCode

存储静态的SQL语句。

package org.example.config;

import org.springframework.context.annotation.Configuration;

@Configuration
public class PostgreSQLStaticCode {
    /**
     * 4中函数参数类型：有参有返、有参无返...
     * 获取函数的定义
     * @return
     */
    public String getFourCreateFunctionSQL(){
        return
                "**基本语法**\n\n" +
                "```sql\n" +
                "CREATE [ OR REPLACE ] FUNCTION function_name ( [ parameter_name parameter_type [, ...] ] )\n" +
                "    RETURNS return_type\n" +
                "    LANGUAGE plpgsql  -- 或其他支持的语言（如 SQL、Python 等）\n" +
                "AS $$\n" +
                "DECLARE\n" +
                "    -- 可选的变量声明\n" +
                "BEGIN\n" +
                "    -- 函数体：包含 SQL 语句、控制结构（IF、FOR 循环等）等\n" +
                "END $$;\n" +
                "```\n\n" +
                "> - `CREATE FUNCTION`: 创建一个新函数或替换现有的同名函数（使用 `OR REPLACE`）。\n" +
                "> - `function_name`: 函数名，用于在调用时标识和执行函数。\n" +
                "> - `parameter_name parameter_type`: 函数的输入参数，可以有多个参数，每个参数由名称和类型定义。\n" +
                "> - `RETURNS return_type`: 函数返回的数据类型。\n" +
                "> - `LANGUAGE`: 指定函数使用的编程语言，常见的是 `plpgsql`（PostgreSQL 的内置过程化语言）、`sql`（仅包含 SQL 语句的函数）、`plpythonu`（Python 函数，需安装插件支持）等。\n" +
                "> - `AS $$ ... $$`: 函数体的开始和结束标记，`$$` 之间是函数的实际代码部分。\n\n" +
                "### 1 无参无返\n\n" +
                "```sql\n" +
                "CREATE OR REPLACE FUNCTION fun_add()\n" +
                "    RETURNS void\n" +
                "    LANGUAGE plpgsql\n" +
                "AS $$\n" +
                "DECLARE\n" +
                "BEGIN\n" +
                "    UPDATE \"T_FROM\"\n" +
                "    SET \"Name\" = '111'\n" +
                "    WHERE \"ID\" = 1;\n" +
                "END;$$;\n\n" +
                "-- 调用函数\n" +
                "SELECT * FROM fun_add();\n" +
                "```\n\n" +
                "### 2 无参有返\n\n" +
                "```sql\n" +
                "CREATE OR REPLACE FUNCTION fun_add()\n" +
                "    RETURNS INTEGER\n" +
                "    LANGUAGE plpgsql\n" +
                "AS $$\n" +
                "DECLARE\n" +
                "BEGIN\n" +
                "    RETURN 1 + 2;\n" +
                "END;$$;\n\n" +
                "-- 调用函数\n" +
                "SELECT * FROM fun_add();\n" +
                "```\n\n" +
                "### 3 有参无返\n\n" +
                "```sql\n" +
                "CREATE OR REPLACE FUNCTION fun_add( a int, b text)\n" +
                "    RETURNS void\n" +
                "    LANGUAGE plpgsql\n" +
                "AS $$\n" +
                "DECLARE\n" +
                "BEGIN\n" +
                "    UPDATE \"T_FROM\"\n" +
                "    SET \"Name\" = b\n" +
                "    WHERE \"ID\" = a;\n" +
                "END;$$;\n\n" +
                "-- 调用函数\n" +
                "SELECT * FROM fun_add();\n" +
                "```\n\n" +
                "### ==4 有参有返==\n\n" +
                "**返回一个值**\n\n" +
                "```sql\n" +
                "CREATE OR REPLACE FUNCTION fun_add( a int, b int)\n" +
                "    RETURNS INTEGER\n" +
                "    LANGUAGE plpgsql\n" +
                "AS $$\n" +
                "DECLARE\n" +
                "    c INT;\n" +
                "BEGIN\n" +
                "    -- 给变量赋值\n" +
                "    c:= a + b;\n" +
                "    RETURN c;\n" +
                "END;$$;\n\n" +
                "-- 调用函数\n" +
                "SELECT * FROM fun_add( 1,2 );\n" +
                "```\n\n" +
                "**返回一个表**\n\n" +
                "```SQL\n" +
                "-- 创建 加法函数\n" +
                "CREATE OR REPLACE FUNCTION testfun ( a INT ) \n" +
                "    RETURNS TABLE( id INTEGER,name varchar(20)) \n" +
                "    LANGUAGE plpgsql \n" +
                "AS $$ \n" +
                "DECLARE\n" +
                "BEGIN\n" +
                "    -- 数据处理\n" +
                "    CREATE TEMP TABLE TEMP_T_FROM AS\n" +
                "    (\n" +
                "        SELECT \n" +
                "            \"ID\",\n" +
                "            \"Name\" \n" +
                "        FROM \"T_FROM\" \n" +
                "        WHERE \"ID\" = a\n" +
                "    );\n" +
                "    UPDATE TEMP_T_FROM SET \"Name\" = '修改后';\n" +
                "    -- 返回查询结果\n" +
                "    RETURN QUERY\n" +
                "    SELECT \"ID\",\"Name\" FROM TEMP_T_FROM;\n" +
                "    -- 删除临时表(如果有创建临时表就在最后删除)\n" +
                "    DROP TABLE IF EXISTS TEMP_T_FROM;\n" +
                "END; $$;\n\n" +
                "-- 调用函数\n" +
                "-- SELECT * FROM testfun (1)\n\n" +
                "-- 删除函数\n" +
                "-- DROP FUNCTION testfun(INT);\n" +
                "```\n\n" +
                "### 获取函数定义\n\n" +
                "```sql\n" +
                "SELECT   \n" +
                "    proname,\n" +
                "    prosrc AS function_definition,\n" +
                "    pg_get_functiondef(p.oid) AS function_definition\n" +
                "FROM   \n" +
                "    pg_proc p\n" +
                "WHERE   \n" +
                "    proname ilike 'QUERT_TO_FunDetails'    -- 函数名\n" +
                "--    AND pronamespace = (SELECT oid FROM pg_namespace WHERE nspname = 'your_schema_name');\n" +
                "```\n\n" +
                "> - **`prosrc AS function_definition`**：返回函数的源代码（即函数体的 SQL 定义）。\n" +
                "> - **`pg_get_functiondef(p.oid) AS function_definition`**：返回函数的完整 SQL 创建定义（包含更多的元数据，如参数类型、返回类型等）。";

    }

    /**
     * 测试方法
     * 
     * @return
     */
    public String getTest() {
        String sqlCode =
                "# Example Function\n" +
                "```sql\n" +
                "CREATE FUNCTION example() RETURNS void AS $$ BEGIN END; $$;\n";
        return sqlCode;
    }
}

controller

package org.example.controller;

import org.example.config.MarkdownToHtmlConverter;
import org.example.config.PostgreSQLStaticCode;
import org.example.service.FunctionService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;

@RestController
@RequestMapping("/api")
public class FunctionController {
    @Autowired
    public MarkdownToHtmlConverter markdownToHtmlConverter;


    @GetMapping(value = "/getFourCreateFunctionSQL", produces = "text/html;charset=UTF-8")
    public String fourCreateFunctionSQL(){
        String fourCreateFunctionSQL = postgreSQLStaticCode.getFourCreateFunctionSQL();
        return markdownToHtmlConverter.convert(fourCreateFunctionSQL);
    }


}

PostgreSQLApplication启动类

package org.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class PostgreSQLApplication {
    public static void main(String[] args) {
        SpringApplication.run(PostgreSQLApplication.class, args);
    }
}

application.yml

server:
  port: 8080

请求地址测试

http://localhost:8080/api/getFourCreateFunctionSQL

结果：