Add demo for SlotChainBuilder SPI

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-demo/pom.xml

@@ -27,6 +27,7 @@
         <module>sentinel-demo-apollo-datasource</module>
         <module>sentinel-demo-annotation-spring-aop</module>
         <module>sentinel-demo-parameter-flow-control</module>
+        <module>sentinel-demo-slot-chain-spi</module>
     </modules>
 
     <dependencies>

sentinel-demo/sentinel-demo-slot-chain-spi/pom.xml

@@ -0,0 +1,14 @@
+<?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">
+    <parent>
+        <artifactId>sentinel-demo</artifactId>
+        <groupId>com.alibaba.csp</groupId>
+        <version>0.2.1-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>sentinel-demo-slot-chain-spi</artifactId>
+
+</project>

sentinel-demo/sentinel-demo-slot-chain-spi/src/main/java/com/alibaba/csp/sentinel/demo/slot/DemoSlot.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.csp.sentinel.demo.slot;
+
+import com.alibaba.csp.sentinel.context.Context;
+import com.alibaba.csp.sentinel.node.DefaultNode;
+import com.alibaba.csp.sentinel.slotchain.AbstractLinkedProcessorSlot;
+import com.alibaba.csp.sentinel.slotchain.ResourceWrapper;
+
+/**
+ * An example slot that records current context and entry resource.
+ *
+ * @author Eric Zhao
+ */
+public class DemoSlot extends AbstractLinkedProcessorSlot<DefaultNode> {
+
+    @Override
+    public void entry(Context context, ResourceWrapper resourceWrapper, DefaultNode node, int count, Object... args)
+        throws Throwable {
+        System.out.println("Current context: " + context.getName());
+        System.out.println("Current entry resource: " + context.getCurEntry().getResourceWrapper().getName());
+
+        fireEntry(context, resourceWrapper, node, count, args);
+    }
+
+    @Override
+    public void exit(Context context, ResourceWrapper resourceWrapper, int count, Object... args) {
+        System.out.println("Exiting for entry on DemoSlot: " + context.getCurEntry().getResourceWrapper().getName());
+
+        fireExit(context, resourceWrapper, count, args);
+    }
+}

sentinel-demo/sentinel-demo-slot-chain-spi/src/main/java/com/alibaba/csp/sentinel/demo/slot/DemoSlotChainBuilder.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.csp.sentinel.demo.slot;
+
+import com.alibaba.csp.sentinel.slotchain.ProcessorSlotChain;
+import com.alibaba.csp.sentinel.slotchain.SlotChainBuilder;
+import com.alibaba.csp.sentinel.slots.DefaultSlotChainBuilder;
+
+/**
+ * An example slot chain builder. To activate this slot chain builder,
+ * add the class name to corresponding SPI file in `resource/META-INF/services` directory.
+ *
+ * @author Eric Zhao
+ */
+public class DemoSlotChainBuilder implements SlotChainBuilder {
+
+    @Override
+    public ProcessorSlotChain build() {
+        ProcessorSlotChain chain = new DefaultSlotChainBuilder().build();
+        chain.addLast(new DemoSlot());
+        return chain;
+    }
+}

sentinel-demo/sentinel-demo-slot-chain-spi/src/main/java/com/alibaba/csp/sentinel/demo/slot/SlotChainBuilderSpiDemo.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.csp.sentinel.demo.slot;
+
+import com.alibaba.csp.sentinel.Entry;
+import com.alibaba.csp.sentinel.SphU;
+import com.alibaba.csp.sentinel.slots.block.BlockException;
+
+/**
+ * @author Eric Zhao
+ */
+public class SlotChainBuilderSpiDemo {
+
+    public static void main(String[] args) {
+        // You will see this in record.log, indicating that the custom slot chain builder is activated:
+        // [SlotChainProvider] Global slot chain builder resolved: com.alibaba.csp.sentinel.demo.slot.DemoSlotChainBuilder
+        Entry entry = null;
+        try {
+            entry = SphU.entry("abc");
+        } catch (BlockException ex) {
+            ex.printStackTrace();
+        } finally {
+            if (entry != null) {
+                entry.exit();
+            }
+        }
+    }
+}

sentinel-demo/sentinel-demo-slot-chain-spi/src/main/resources/META-INF/services/com.alibaba.csp.sentinel.slotchain.SlotChainBuilder

@@ -0,0 +1,2 @@
+# Custom slot chain builder
+com.alibaba.csp.sentinel.demo.slot.DemoSlotChainBuilder