dynamic validations on Export API

learn/how-tos/validationson-exportapi-using-crudlisteners.md

@@ -0,0 +1,141 @@
+---
+title: "Dynamic Validations on Export API using CRUD Listeners"
+id: "validationson-exportapi-using-crudListeners"
+sidebar_label: "Validations using CRUD Listeners on Export API"
+---
+## Introduction
+
+In this document, learn how we can implement dynamic validations on Export API.
+
+The existing listeners are designed specifically for dynamic validations during CRUD operations. To perform dynamic validations on the Export API, we need to incorporate a new listener for export operations. To achieve this, include the following Java classes: EntityPreExportEvent.java and ExportMethodInvocationHandler.java. Place these classes in the 'src/main/java/com/wavemaker/runtime/data/aop' directory, ensuring you create the necessary package/folder structure under 'src/main/java'.
+
+EntityPreExportEvent class:
+
+```java
+package com.wavemaker.runtime.data.aop;
+
+import com.wavemaker.runtime.data.event.EntityCRUDEvent;
+import com.wavemaker.runtime.data.export.DataExportOptions;
+
+public class EntityPreExportEvent<E> extends EntityCRUDEvent<E> {
+    private DataExportOptions dataExportOptions;
+    public EntityPreExportEvent(String serviceId, Class<E> entityClass, DataExportOptions dataExportOptions) {
+        super(serviceId, entityClass);
+        this.dataExportOptions = dataExportOptions;
+    }
+
+    public DataExportOptions getDataExportOptions() {
+        return dataExportOptions;
+    }
+}
+```
+
+ExportMethodInvocationHandler class:
+
+```java
+package com.wavemaker.runtime.data.aop;
+
+import com.wavemaker.runtime.data.export.DataExportOptions;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationEventPublisher;
+
+import java.lang.reflect.Method;
+import java.util.Objects;
+
+public class ExportMethodInvocationHandler implements CRUDMethodInvocationHandler {
+    private static final Logger logger = LoggerFactory.getLogger(ExportMethodInvocationHandler.class);
+
+    @Autowired
+    private ApplicationEventPublisher applicationEventPublisher;
+
+    @Override
+    public void preHandle(String serviceId, Class entityClass, Method method, Object[] args) {
+        DataExportOptions dataExportOptions = (DataExportOptions) args[0];
+        logger.info("publishing pre export event");
+        applicationEventPublisher.publishEvent(new EntityPreExportEvent(serviceId, entityClass, dataExportOptions));
+    }
+
+    @Override
+    public void postHandle(String serviceId, Class entityClass, Method method, Object retVal) {
+    }
+
+    @Override
+    public boolean matches(Class entityClass, Method method) {
+        boolean matches = "export".equals(method.getName()) && Objects.equals(method.getParameterTypes()[0].getName(), DataExportOptions.class.getName());
+        logger.info("export matches: {}, method name: {}, param1: {}", matches, method.getName(), method.getParameterTypes()[0].getName());
+        return matches;
+    }
+}
+
+```
+
+Create a bean in project-user-spring.xml file for ExportMethodInvocationHandler class.
+
+``` bean
+<bean name="ExportEventHandler" class="com.wavemaker.runtime.data.aop.ExportMethodInvocationHandler"/>
+
+```
+
+Now you can use the EntityPreExportEvent listener in your Java services as per your requirement. 
+
+Follow the below example in which we are validating the user role and providing export access specifically to the admin role for exporting data table content.
+
+1. Create a JavaService.
+
+```java
+package com.testcrud.agecalculator;
+import javax.servlet.http.HttpServletRequest;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import com.wavemaker.runtime.security.SecurityService;
+import com.wavemaker.runtime.service.annotations.ExposeToClient;
+import com.wavemaker.runtime.service.annotations.HideFromClient;
+import java.sql.Date;
+import java.time.Period;
+import java.time.LocalDate;
+import javax.servlet.http.HttpServletRequest;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import com.wavemaker.runtime.service.annotations.ExposeToClient;
+import com.wavemaker.runtime.service.annotations.HideFromClient;
+import org.springframework.context.event.EventListener;
+import com.testcrud.hrdb.Employee;
+import com.testcrud.hrdb.User;
+import com.testcrud.hrdb.service.UserService;
+import com.wavemaker.runtime.security.SecurityService;
+import com.wavemaker.commons.WMRuntimeException;
+import com.wavemaker.runtime.data.aop.EntityPreExportEvent;
+import com.wavemaker.commons.MessageResource;
+import com.wavemaker.commons.WMRuntimeException;
+import com.wavemaker.commons.MessageResource;
+import com.wavemaker.commons.WMRuntimeException;
+import java.util.*;
+
+@ExposeToClient
+public class Exportapivalidations {
+    @Autowired
+    private UserService userService;
+     @Autowired
+    SecurityService securityService;
+
+
+    private static final Logger logger = LoggerFactory.getLogger(AgeCalculator.class);
+
+   @EventListener
+   public void beforeEmployeeCreate(EntityPreExportEvent<User> entityPreExportEvent){
+
+       logger.info("---------Pre Processing-----------");
+        final List userRoles = (List) Arrays.asList(securityService.getUserRoles());
+        if (!userRoles.contains("admin")) {
+            logger.error("The logged in user does not have enough permissions");
+            throw new WMRuntimeException(MessageResource.create("You do not have enough permissions"));
+        } 
+
+   }
+
+}
+
+ ```

website/sidebars.json

@@ -926,6 +926,7 @@
 				"how-tos/audit-history-using-crud-listeners",
 				"how-tos/rowlevel-security-using-crud-event-listeners",
 				"how-tos/validations-using-crudListeners",
+				"how-tos/validationson-exportapi-using-crudListeners",
 				"how-tos/custom-business-logic-using-crud-event-listeners",
 				"how-tos/mysql-connection-using-ssl",
 				"how-tos/switch-mariadb-to-mysql-connector"