Provides a Jinja2 implementation for TemplateRenderer

pom.xml

@@ -34,6 +34,7 @@
 		<module>spring-ai-bom</module>
 		<module>spring-ai-commons</module>
 		<module>spring-ai-template-st</module>
+		<module>spring-ai-template-jinja</module>
 		<module>spring-ai-client-chat</module>
 		<module>spring-ai-model</module>
 		<module>spring-ai-test</module>

spring-ai-bom/pom.xml

@@ -101,6 +101,12 @@
 				<version>${project.version}</version>
 			</dependency>
 
+			<dependency>
+				<groupId>org.springframework.ai</groupId>
+				<artifactId>spring-ai-template-jinja</artifactId>
+				<version>${project.version}</version>
+			</dependency>
+
 			<!-- Spring AI model -->
 
 			<dependency>

spring-ai-model/pom.xml

@@ -53,6 +53,12 @@
 			<version>${project.parent.version}</version>
 		</dependency>
 
+		<dependency>
+			<groupId>org.springframework.ai</groupId>
+			<artifactId>spring-ai-template-jinja</artifactId>
+			<version>${project.parent.version}</version>
+		</dependency>
+
 		<dependency>
 			<groupId>io.micrometer</groupId>
 			<artifactId>micrometer-observation</artifactId>

spring-ai-template-jinja/pom.xml

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2023-2025 the original author or authors.
+  ~
+  ~ 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
+  ~
+  ~      https://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.
+  -->
+
+<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>
+	<parent>
+		<groupId>org.springframework.ai</groupId>
+		<artifactId>spring-ai-parent</artifactId>
+		<version>1.1.0-SNAPSHOT</version>
+	</parent>
+	<artifactId>spring-ai-template-jinja</artifactId>
+	<packaging>jar</packaging>
+	<name>Spring AI Template Jinja</name>
+	<description>Jinja implementation for Spring AI templating</description>
+	<url>https://github.com/spring-projects/spring-ai</url>
+
+	<scm>
+		<url>https://github.com/spring-projects/spring-ai</url>
+		<connection>git://github.com/spring-projects/spring-ai.git</connection>
+		<developerConnection>[email protected]:spring-projects/spring-ai.git</developerConnection>
+	</scm>
+
+	<properties>
+		<maven.compiler.source>17</maven.compiler.source>
+		<maven.compiler.target>17</maven.compiler.target>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.ai</groupId>
+			<artifactId>spring-ai-commons</artifactId>
+			<version>${project.parent.version}</version>
+		</dependency>
+
+		<dependency>
+			<groupId>com.hubspot.jinjava</groupId>
+			<artifactId>jinjava</artifactId>
+			<version>2.8.0</version>
+		</dependency>
+
+		<!-- Logging -->
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-api</artifactId>
+		</dependency>
+
+		<!-- test dependencies -->
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+</project>

spring-ai-template-jinja/src/main/java/org/springframework/ai/template/jinja/JinjaTemplateRenderer.java

@@ -0,0 +1,172 @@
+/*
+ * Copyright 2023-2025 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 org.springframework.ai.template.jinja;
+
+import com.hubspot.jinjava.Jinjava;
+import com.hubspot.jinjava.JinjavaConfig;
+import com.hubspot.jinjava.tree.parse.ExpressionToken;
+import com.hubspot.jinjava.tree.parse.Token;
+import com.hubspot.jinjava.tree.parse.TokenScanner;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.ai.template.TemplateRenderer;
+import org.springframework.ai.template.ValidationMode;
+import org.springframework.util.Assert;
+
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Renders a template using the Jin-java library.
+ *
+ * <p>
+ * This renderer allows customization of validation behavior.
+ *
+ * <p>
+ * Use the {@link #builder()} to create and configure instances.
+ *
+ * <p>
+ * <b>Thread safety:</b> This class is safe for concurrent use. Each call to
+ * {@link #apply(String, Map)} creates a new Jin-java instance, and no mutable state is
+ * shared between threads.
+ *
+ * @author Sun Yuhan
+ * @since 1.1.0
+ */
+public class JinjaTemplateRenderer implements TemplateRenderer {
+
+	private static final Logger logger = LoggerFactory.getLogger(JinjaTemplateRenderer.class);
+
+	private static final String VALIDATION_MESSAGE = "Not all variables were replaced in the template. Missing variable names are: %s.";
+
+	private static final ValidationMode DEFAULT_VALIDATION_MODE = ValidationMode.THROW;
+
+	private final ValidationMode validationMode;
+
+	/**
+	 * Constructs a new {@code JinjaTemplateRenderer} with the specified validation mode.
+	 * @param validationMode the mode to use for template variable validation; must not be
+	 * null
+	 */
+	public JinjaTemplateRenderer(ValidationMode validationMode) {
+		Assert.notNull(validationMode, "validationMode cannot be null");
+		this.validationMode = validationMode;
+	}
+
+	@Override
+	public String apply(String template, Map<String, Object> variables) {
+		Assert.hasText(template, "template cannot be null or empty");
+		Assert.notNull(variables, "variables cannot be null");
+		Assert.noNullElements(variables.keySet(), "variables keys cannot be null");
+
+		if (this.validationMode != ValidationMode.NONE) {
+			validate(template, variables);
+		}
+		Jinjava jinjava = new Jinjava();
+		String rendered;
+		try {
+			rendered = jinjava.render(template, variables);
+		}
+		catch (Exception ex) {
+			throw new IllegalArgumentException("The template string is not valid.", ex);
+		}
+		return rendered;
+	}
+
+	/**
+	 * Validates that all required template variables are provided in the model. Returns
+	 * the set of missing variables for further handling or logging.
+	 * @param template the template to be rendered
+	 * @param templateVariables the provided variables
+	 * @return set of missing variable names, or empty set if none are missing
+	 */
+	private Set<String> validate(String template, Map<String, Object> templateVariables) {
+		Set<String> templateTokens = getInputVariables(template);
+		Set<String> modelKeys = templateVariables.keySet();
+		Set<String> missingVariables = new HashSet<>(templateTokens);
+		missingVariables.removeAll(modelKeys);
+
+		if (!missingVariables.isEmpty()) {
+			if (this.validationMode == ValidationMode.WARN) {
+				logger.warn(VALIDATION_MESSAGE.formatted(missingVariables));
+			}
+			else if (this.validationMode == ValidationMode.THROW) {
+				throw new IllegalStateException(VALIDATION_MESSAGE.formatted(missingVariables));
+			}
+		}
+		return missingVariables;
+	}
+
+	/**
+	 * Retrieve all variables in the template
+	 * @param template the template to be rendered
+	 * @return set of variable names
+	 */
+	private Set<String> getInputVariables(String template) {
+		Set<String> variables = new HashSet<>();
+		JinjavaConfig config = JinjavaConfig.newBuilder().build();
+		TokenScanner scanner = new TokenScanner(template, config);
+
+		while (scanner.hasNext()) {
+			Token token = scanner.next();
+			if (token instanceof ExpressionToken expressionToken) {
+				String varName = expressionToken.getExpr().trim();
+				variables.add(varName);
+			}
+		}
+		return variables;
+	}
+
+	public static Builder builder() {
+		return new Builder();
+	}
+
+	/**
+	 * Builder for configuring and creating {@link JinjaTemplateRenderer} instances.
+	 */
+	public static final class Builder {
+
+		private ValidationMode validationMode = DEFAULT_VALIDATION_MODE;
+
+		private Builder() {
+		}
+
+		/**
+		 * Sets the validation mode to control behavior when the provided variables do not
+		 * match the variables required by the template. Default is
+		 * {@link ValidationMode#THROW}.
+		 * @param validationMode The desired validation mode.
+		 * @return This builder instance for chaining.
+		 */
+		public Builder validationMode(ValidationMode validationMode) {
+			this.validationMode = validationMode;
+			return this;
+		}
+
+		/**
+		 * Builds and returns a new {@link JinjaTemplateRenderer} instance with the
+		 * configured settings.
+		 * @return A configured {@link JinjaTemplateRenderer}.
+		 */
+		public JinjaTemplateRenderer build() {
+			return new JinjaTemplateRenderer(this.validationMode);
+		}
+
+	}
+
+}

spring-ai-template-jinja/src/main/java/org/springframework/ai/template/jinja/package-info.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2023-2025 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.
+ */
+
+@NonNullApi
+@NonNullFields
+package org.springframework.ai.template.jinja;
+
+import org.springframework.lang.NonNullApi;
+import org.springframework.lang.NonNullFields;