[BAEL-9235] - Introduction to MVEL

libraries-7/pom.xml

@@ -63,6 +63,11 @@
             <artifactId>webmagic-extension</artifactId>
             <version>1.0.3</version>
         </dependency>
+        <dependency>
+            <groupId>org.mvel</groupId>
+            <artifactId>mvel2</artifactId>
+            <version>${mvel.version}</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -104,6 +109,7 @@
         <manifold.version>2024.1.20</manifold.version>
         <record-builder.version>47</record-builder.version>
         <jena.version>5.5.0</jena.version>
+        <mvel.version>2.5.2.Final</mvel.version>
     </properties>
 
 </project>

libraries-7/src/main/java/com/baeldung/mvel/model/Employee.java

@@ -0,0 +1,85 @@
+package com.baeldung.mvel.model;
+
+public class Employee {
+    private String name;
+    private Job job;
+
+    public Employee(String name, Job job) {
+        this.name = name;
+        this.job = job;
+    }
+
+    public Employee(String name, int experienceInYears, double salary, String department) {
+        this.name = name;
+        this.job = new Job(experienceInYears, salary, department);
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public void setJob(Job job) {
+        this.job = job;
+    }
+
+    public Job getJob() {
+        return job;
+    }
+
+
+    public static class Job {
+        private int experienceInYears;
+        private double salary;
+        private String department;
+
+        public Job(int experienceInYears, double salary) {
+            this.experienceInYears = experienceInYears;
+            this.salary = salary;
+        }
+
+        public Job(int experienceInYears, double salary, String department) {
+            this.experienceInYears = experienceInYears;
+            this.salary = salary;
+            this.department = department;
+        }
+
+        public int getExperienceInYears() {
+            return experienceInYears;
+        }
+
+        public void setExperienceInYears(int experienceInYears) {
+            this.experienceInYears = experienceInYears;
+        }
+
+        public double getSalary() {
+            return salary;
+        }
+
+        public void setSalary(double salary) {
+            this.salary = salary;
+        }
+
+        public String getDepartment() {
+            return department;
+        }
+
+        public void setDepartment(String department) {
+            this.department = department;
+        }
+
+        public double calculateAnnualBonus() {
+            if (experienceInYears > 10) {
+                return salary * 0.20;
+            } else if (experienceInYears > 5) {
+                return salary * 0.10;
+            } else {
+                return salary * 0.05;
+            }
+        }
+    }
+
+}

libraries-7/src/test/java/com/baeldung/mvel/MvelServiceUnitTest.java

@@ -0,0 +1,143 @@
+package com.baeldung.mvel;
+
+import org.junit.jupiter.api.Test;
+import org.mvel2.*;
+
+import java.io.Serializable;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.baeldung.mvel.model.Employee;
+
+public class MvelServiceUnitTest {
+
+    @Test
+    public void givenSimpleExpression_whenEvaluate_thenCorrectResult() {
+        String expression = "5 + 3 * 2";
+        Object result = MVEL.eval(expression);
+
+        assertEquals(11, result);
+    }
+
+    @Test
+    public void givenVariables_whenEvaluateExpression_thenCorrectResult() {
+        Map<String, Object> variables = new HashMap<>();
+        variables.put("salary", 75000.0);
+        variables.put("experience", 8);
+
+        String expression = "salary * 0.10";
+        Object result = MVEL.eval(expression, variables);
+
+        assertEquals(7500.0, result);
+    }
+
+    @Test
+    public void givenBooleanExpression_whenEvaluate_thenCorrectResult() {
+        Map<String, Object> variables = new HashMap<>();
+        variables.put("experience", 12);
+        variables.put("salary", 95000.0);
+
+        String expression = "experience > 10 && salary > 80000";
+        Object result = MVEL.eval(expression, variables);
+
+        assertTrue((Boolean) result);
+    }
+
+    @Test
+    public void givenNullSafeNavigation_whenPropertyIsNull_thenNoException() {
+        Employee.Job job = new Employee.Job(5, 5000);
+        Employee employee = new Employee("David", job);
+        employee.getJob()
+            .setDepartment(null);
+        String expression = " (job.?department.length) ";
+        Object result = MVEL.eval(expression, employee);
+
+        assertNull(result);
+    }
+
+    @Test
+    public void givenEmployee_whenAccessProperties_thenCorrectValues() {
+        Employee.Job job = new Employee.Job(8, 75000.0);
+        Employee employee = new Employee("John Doe", job);
+
+        String expression = "name + ' has ' + job.experienceInYears + ' years of experience'";
+        Object result = MVEL.eval(expression, employee);
+
+        assertEquals("John Doe has 8 years of experience", result);
+    }
+
+    @Test
+    public void givenEmployee_whenCallMethod_thenCorrectResult() {
+        Employee.Job job = new Employee.Job(12, 90000.0);
+        Employee employee = new Employee("Jane Smith", job);
+
+        String expression = "job.calculateAnnualBonus()";
+        Object result = MVEL.eval(expression, employee);
+
+        assertEquals(18000.0, (Double) result, 0.01);
+    }
+
+    @Test
+    public void givenEmployee_whenEvaluateConditional_thenCorrectResult() {
+        Employee.Job job = new Employee.Job(15, 120000.0);
+        Employee employee = new Employee("Bob Johnson", job);
+
+        String expression = "if (job.experienceInYears > 10) { job.salary * 0.20 } " + "else if (job.experienceInYears > 5) { job.salary * 0.10 } " +
+            "else { job.salary * 0.05 }";
+        Object result = MVEL.eval(expression, employee);
+
+        assertEquals(24000.0, (Double) result, 0.01);
+    }
+
+    @Test
+    public void givenCompiledExpression_whenExecuteMultipleTimes_thenCorrectResults() {
+        String expression = "job.experienceInYears > 5 && job.salary > 50000";
+        Serializable compiledExpression = MVEL.compileExpression(expression);
+
+        Employee.Job job1 = new Employee.Job(7, 60000.0);
+        Employee employee1 = new Employee("Alice", job1);
+
+        Employee.Job job2 = new Employee.Job(3, 45000.0);
+        Employee employee2 = new Employee("Charlie", job2);
+
+        boolean result1 = (Boolean) MVEL.executeExpression(compiledExpression, employee1);
+        boolean result2 = (Boolean) MVEL.executeExpression(compiledExpression, employee2);
+
+        assertTrue(result1);
+        assertFalse(result2);
+    }
+
+    @Test
+    public void givenListProjection_whenFilter_thenCorrectResult() {
+        Map<String, Object> variables = new HashMap<>();
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+        variables.put("numbers", numbers);
+
+        String expression = "($ in numbers if $ > 5)";
+        Object result = MVEL.eval(expression, variables);
+
+        assertInstanceOf(List.class, result);
+        List<?> filteredList = (List<?>) result;
+        assertEquals(5, filteredList.size());
+    }
+
+    @Test
+    public void givenListTransformation_whenProject_thenCorrectResult() {
+        Map<String, Object> variables = new HashMap<>();
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
+        variables.put("numbers", numbers);
+
+        String expression = "($ * 2 in numbers)";
+        Object result = MVEL.eval(expression, variables);
+
+        assertInstanceOf(List.class, result);
+        List<?> transformedList = (List<?>) result;
+        assertEquals(10, transformedList.get(4));
+    }
+
+}
+

libraries-7/src/test/java/com/baeldung/mvel/MvelTemplateServiceUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.mvel;
+
+import com.baeldung.mvel.model.Employee;
+
+import org.junit.jupiter.api.Test;
+import org.mvel2.templates.CompiledTemplate;
+import org.mvel2.templates.TemplateCompiler;
+import org.mvel2.templates.TemplateRuntime;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class MvelTemplateServiceUnitTest {
+
+    @Test
+    public void givenEmployeeData_whenGenerateReport_thenCorrectOutput() {
+        String template = """
+            Employee Report
+            ================
+            Name: @{name}
+            Experience: @{experience} years
+            Salary: $@{salary
+            """;
+
+        Map<String, Object> variables = new HashMap<>();
+        variables.put("name", "John Doe");
+        variables.put("experience", 12);
+        variables.put("salary", 95000.0);
+
+        CompiledTemplate compiledTemplate = TemplateCompiler.compileTemplate(template);
+        String result = (String) TemplateRuntime.execute(compiledTemplate, variables);
+
+        assertTrue(result.contains("John Doe"));
+        assertTrue(result.contains("12 years"));
+    }
+
+    @Test
+    public void givenSeniorEmployee_whenGenerateReport_thenCorrectStatus() {
+        String template = """
+            Employee Report
+            @if{experience > 10}
+            Status: Senior Employee\n
+            @else{}
+            Status: Junior/Mid-level Employee
+            @end{}
+            """;
+
+        Map<String, Object> variables = new HashMap<>();
+        variables.put("experience", 12);
+
+        CompiledTemplate compiledTemplate = TemplateCompiler.compileTemplate(template);
+        String result = (String) TemplateRuntime.execute(compiledTemplate, variables);
+
+        assertTrue(result.contains("Senior Employee"));
+    }
+
+    @Test
+    public void givenEmployeeList_whenGenerateListReport_thenCorrectOutput() {
+        String template = """
+            "Employee List:
+            "@foreach{emp : employees}
+            "- @{emp.name} (@{emp.job.department})
+            "@end{}
+            """;
+
+        List<Employee> employees = Arrays.asList(new Employee("John", 10, 80000.0, "IT"), new Employee("Jane", 8, 75000.0, "HR"),
+            new Employee("Bob", 12, 95000.0, "Finance"));
+
+        Map<String, Object> variables = new HashMap<>();
+        variables.put("employees", employees);
+
+        CompiledTemplate compiledTemplate = TemplateCompiler.compileTemplate(template);
+        String result = (String) TemplateRuntime.execute(compiledTemplate, variables);
+
+        assertTrue(result.contains("John (IT)"));
+        assertTrue(result.contains("Jane (HR)"));
+    }
+}
+