feat: improve the README (#9)

Author: sukidayou

README.md

@@ -1,27 +1,23 @@
 jcasbin-mongodb-adapter
 ===
-MongoDB policy storage, implemented as an adapter for [jcasbin](https://github.com/casbin/jcasbin).
+[![codebeat badge](https://codebeat.co/badges/df265133-60a0-4ee7-b57d-25fd27273905)](https://codebeat.co/projects/github-com-jcasbin-mongo-adapter-master)
+[![build](https://github.com/jcasbin/jcasbin-mongo-adapter/actions/workflows/maven-ci.yml/badge.svg)](https://github.com/jcasbin/jcasbin-mongo-adapter/actions/workflows/maven-ci.yml)
+[![codecov](https://codecov.io/gh/casbin/jcasbin-mongo-adapter/branch/master/graph/badge.svg)](https://codecov.io/gh/casbin/jcasbin-mongo-adapter)
+[![javadoc](https://javadoc.io/badge2/org.casbin/jcasbin-mongo-adapter/javadoc.svg)](https://javadoc.io/doc/org.casbin/jcasbin-mongo-adapter)
+[![Maven Central](https://img.shields.io/maven-central/v/org.casbin/jcasbin-mongo-adapter.svg)](https://mvnrepository.com/artifact/org.casbin/jcasbin-mongo-adapter/latest)
+[![Discord](https://img.shields.io/discord/1022748306096537660?logo=discord&label=discord&color=5865F2)](https://discord.gg/S5UjpzGZjN)
 
-## Getting Started
+jcasbin-mongodb-adapter is the [MongoDB](https://github.com/mongodb/mongo) adapter for [jCasbin](https://github.com/casbin/jcasbin). With this library, jCasbin can load policy from a MongoDB database or save policy to it.
 
-### maven
-add `jitpack` repository
-```xml
+## Installation
 
-<repositories>
-    <repository>
-        <id>jitpack.io</id>
-        <url>https://jitpack.io</url>
-    </repository>
-</repositories>
-```
-add `jcasbin-mongo-adapter` dependency
-```xml
+For Maven:
 
+```xml
 <dependency>
-    <groupId>com.github.zzl221000</groupId>
+    <groupId>org.casbin</groupId>
     <artifactId>jcasbin-mongo-adapter</artifactId>
-    <version>v1.0</version>
+    <version>LATEST</version>
 </dependency>
 ```
 
@@ -34,42 +30,56 @@ optional: If your project already has a mongodb driver, please ignore it.
 </dependency>
 ```
 
+## Simple Example
+
 ```java
+package org.casbin.adapter;
+
+import com.mongodb.client.MongoClient;
+import com.mongodb.client.MongoClients;
+import com.mongodb.client.MongoDatabase;
+import org.casbin.jcasbin.main.Enforcer;
 import org.casbin.jcasbin.persist.Adapter;
 import org.jim.jcasbin.MongoAdapter;
-import org.casbin.jcasbin.main.Enforcer;
-import org.casbin.jcasbin.main.SyncedEnforcer;
-import org.casbin.jcasbin.model.Model;
-import com.ruiling.system.config.errors.CasbinModelConfigNotFoundException;
 
-public class Demo {
+import java.util.ArrayList;
+
+public class Test {
     public static void main(String[] args) {
-        Adapter adapter = new MongoAdapter(mongoClient, "casbin");
-        Model model = new Model();
-        try {
-            String modelContext = properties.getModelContext();
-            model.loadModelFromText(modelContext);
-        } catch (CasbinModelConfigNotFoundException e) {
-            // use default model configuration 
-            // request definition
-            model.addDef("r", "r", "sub, obj, act");
-            // policy definition
-            model.addDef("p", "p", "sub, obj, act");
-            // role definition
-            model.addDef("g", "g", "_, _");
-            // policy effect
-            model.addDef("e", "e", "some(where (p.eft == allow))");
-            // matchers
-            model.addDef("m", "m", "g(r.sub, p.sub) && r.obj == p.obj && r.act == p.act");
+        // Use MongoDB connection string and database name to initialize a MongoAdapter.
+        String connectionString = "mongodb://localhost:27017/";
+        MongoClient mongoClient = MongoClients.create(connectionString);
+        MongoDatabase database = mongoClient.getDatabase("casbin");
+
+        // Check and create a collection
+        if (!database.listCollectionNames().into(new ArrayList<>()).contains("casbin_rule")) {
+            database.createCollection("casbin_rule");
         }
-        Enforcerenforcer = new SyncedEnforcer(model, adapter);
-        // set auto save policy
-        enforcer.enableAutoSave(true);
-    }
 
+        Adapter adapter = new MongoAdapter(mongoClient, "casbin");
+        Enforcer enforcer = new Enforcer("examples/rbac_model.conf", "examples/rbac_policy.csv");
+
+        // Check the permission.
+        enforcer.enforce("alice", "data1", "read");
+
+        // Modify the policy.
+        // enforcer.addPolicy(...);
+        // enforcer.removePolicy(...);
+
+        // Save the policy back to DB.
+        adapter.savePolicy(enforcer.getModel());
+
+        // Close the MongoDB client.
+        mongoClient.close();
+    }
 }
+
 ```
 
+## Getting Help
+
+- [jCasbin](https://github.com/casbin/jcasbin)
+
 ## License
 
-[Apache-2.0](./LICENSE)
+This project is under Apache 2.0 License. See the [LICENSE](LICENSE) file for the full license text.