code commit for BAEL-4869 (#10812)

* Code commit for "Converting String to BigDecimal in Java" - Article

* modified the assert param for comparing actual and expected values

* removed the conflict change

* Code commit for Secret Key to String and vice versa in java

* renaming the junit class name to match coding standard

* code commit for BAEL-4869

* Adding new module with Secret key to String conversion in Java [BAEL-4489]

* changed code indent by space instead of tab

core-java-modules/core-java-security-3/README.md

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+## Core Java Security
+
+This module contains articles about core Java Security
+
+### Relevant Articles:
+
+- [Secret Key and String Conversion in Java](https://www.baeldung.com/secret-key-and-string-conversion-in-java/)
+- More articles: [[<-- prev]](/core-java-modules/core-java-security-2)

core-java-modules/core-java-security-3/pom.xml

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+<?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">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-security-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-security-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>${commons-codec.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.bouncycastle</groupId>
+            <artifactId>bcprov-jdk15on</artifactId>
+            <version>${bouncycastle.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/javax.xml.bind/jaxb-api -->
+        <dependency>
+            <groupId>javax.xml.bind</groupId>
+            <artifactId>jaxb-api</artifactId>
+            <version>${jaxb-api.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <!-- util -->
+        <bouncycastle.version>1.60</bouncycastle.version>
+        <commons-codec.version>1.11</commons-codec.version>
+        <!-- testing -->
+        <assertj-core.version>3.18.0</assertj-core.version>
+        <jaxb-api.version>2.3.1</jaxb-api.version>
+    </properties>
+
+</project>

core-java-modules/core-java-security-3/src/main/java/com/baeldung/secretkeyandstringconversion/ConversionClassUtil.java

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+package com.baeldung.secretkeyandstringconversion;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.KeySpec;
+import java.util.Base64;
+
+import javax.crypto.KeyGenerator;
+import javax.crypto.SecretKey;
+import javax.crypto.SecretKeyFactory;
+import javax.crypto.spec.PBEKeySpec;
+import javax.crypto.spec.SecretKeySpec;
+
+public class ConversionClassUtil {
+
+    /* Generating Secret key */
+
+    // Generating Secret Key using KeyGenerator class with 256
+    public static SecretKey generateKey(int n) throws NoSuchAlgorithmException {
+        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
+        keyGenerator.init(n);
+        SecretKey originalKey = keyGenerator.generateKey();
+        return originalKey;
+    }
+
+    // Generating Secret Key using password and salt
+    public static SecretKey getKeyFromPassword(String password, String salt)
+            throws NoSuchAlgorithmException, InvalidKeySpecException {
+        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
+        KeySpec spec = new PBEKeySpec(password.toCharArray(), salt.getBytes(), 65536, 256);
+        SecretKey originalKey = new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
+        return originalKey;
+    }
+
+    /* Converting Secret key into String */
+    public static String convertSecretKeyToString(SecretKey secretKey) throws NoSuchAlgorithmException {
+        // Converting the Secret Key into byte array
+        byte[] rawData = secretKey.getEncoded();
+        // Getting String - Base64 encoded version of the Secret Key
+        String encodedKey = Base64.getEncoder().encodeToString(rawData);
+        return encodedKey;
+    }
+
+    /* Converting String into Secret key into */
+    public static SecretKey convertStringToSecretKeyto(String encodedKey) {
+        // Decoding the Base64 encoded string into byte array
+        byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
+        // Rebuilding the Secret Key using SecretKeySpec Class
+        SecretKey originalKey = new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES");
+        return originalKey;
+    }
+
+}

core-java-modules/core-java-security-3/src/test/java/com/baeldung/secretkeyandstringconversion/ConversionClassUtilUnitTest.java

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+package com.baeldung.secretkeyandstringconversion;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+
+import javax.crypto.SecretKey;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ConversionClassUtilUnitTest {
+
+    @Test
+    void givenPasswordAndSalt_whenCreateSecreKeyCheckConversion_thenSuccess()
+            throws NoSuchAlgorithmException, InvalidKeySpecException {
+        // given
+        String password = "Baeldung@2021";
+        String salt = "@$#baelDunG@#^$*";
+
+        // when
+        SecretKey encodedKey = ConversionClassUtil.getKeyFromPassword(password, salt);
+        String encodedString = ConversionClassUtil.convertSecretKeyToString(encodedKey);
+        SecretKey decodeKey = ConversionClassUtil.convertStringToSecretKeyto(encodedString);
+
+        // then
+        Assertions.assertEquals(encodedKey, decodeKey);
+    }
+
+    @Test
+    void givenSize_whenCreateSecreKeyCheckConversion_thenSuccess()
+            throws NoSuchAlgorithmException, InvalidKeySpecException {
+        // given
+        int size = 256;
+
+        // when
+        SecretKey encodedKey = ConversionClassUtil.generateKey(size);
+        String encodedString = ConversionClassUtil.convertSecretKeyToString(encodedKey);
+        SecretKey decodeKey = ConversionClassUtil.convertStringToSecretKeyto(encodedString);
+
+        // then
+        Assertions.assertEquals(encodedKey, decodeKey);
+    }
+
+}

spring-boot-modules/spring-boot-runtime/src/main/java/com/baeldung/sampleapp/config/MaxHTTPHeaderSizeConfig.java

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+package com.baeldung.sampleapp.config;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+@Configuration
+@ComponentScan({ "com.baeldung.sampleapp.web" })
+public class MaxHTTPHeaderSizeConfig implements WebMvcConfigurer {
+
+    public MaxHTTPHeaderSizeConfig() {
+        super();
+    }
+
+}

spring-boot-modules/spring-boot-runtime/src/main/java/com/baeldung/sampleapp/web/controller/MaxHttpHeaderSizeController.java

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+package com.baeldung.sampleapp.web.controller;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping(value = "/request-header-test")
+public class MaxHttpHeaderSizeController {
+
+    @GetMapping
+    public boolean testMaxHTTPHeaderSize(@RequestHeader(value = "token") String token) {
+        return true;
+    }
+
+}

spring-boot-modules/spring-boot-runtime/src/test/java/com/baeldung/web/controller/MaxHttpHeaderSizeControllerIntegrationTest.java

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+package com.baeldung.web.controller;
+
+import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.httpBasic;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.MediaType;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.web.WebAppConfiguration;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.context.WebApplicationContext;
+
+import com.baeldung.sampleapp.config.WebConfig;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = WebConfig.class)
+@WebAppConfiguration
+public class MaxHttpHeaderSizeControllerIntegrationTest {
+
+    private MockMvc mockMvc;
+
+    @Autowired
+    private WebApplicationContext webApplicationContext;
+
+    @Before
+    public void setUp() {
+        mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext).build();
+    }
+
+    @Test
+    public void givenTokenWithLessThan8KBLegth_whenSendGetRequest_thenReturnsOK() throws Exception {
+        mockMvc.perform(get("/request-header-test").contentType(MediaType.APPLICATION_JSON_VALUE)
+                .with(httpBasic("user", "password")).header("token", "token")).andExpect(status().isOk());
+    }
+
+    @Test
+    public void givenTokenIsMissingInHeade_whenSendGetRequest_thenThrowsBadRequest() throws Exception {
+        mockMvc.perform(get("/request-header-test").contentType(MediaType.APPLICATION_JSON_VALUE)
+                .with(httpBasic("user", "password"))).andExpect(status().isBadRequest());
+    }
+
+}

spring-boot-modules/spring-boot-runtime/src/test/java/com/baeldung/web/controller/MaxHttpHeaderSizeControllerLiveTest.java

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+package com.baeldung.web.controller;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.ResponseEntity;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+import org.springframework.web.client.HttpClientErrorException;
+import org.springframework.web.client.RestTemplate;
+
+import com.baeldung.sampleapp.config.MaxHTTPHeaderSizeConfig;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = { MaxHTTPHeaderSizeConfig.class }, loader = AnnotationConfigContextLoader.class)
+@ActiveProfiles("test")
+// Start MaxHttpHeaderSizeController Spring Boot App(MainApplication) first
+public class MaxHttpHeaderSizeControllerLiveTest {
+
+    @Test(expected = HttpClientErrorException.class)
+    public void givenTokenWithGreaterThan8KBLegth_whenSendGetRequest_thenThrowsBadRequest() throws Exception {
+        final String url = "http://localhost:8080/request-header-test";
+        HttpHeaders headers = new HttpHeaders();
+        headers.set("token", readRandomStringFromFile());
+
+        HttpEntity entity = new HttpEntity(headers);
+        final ResponseEntity<String> response = new RestTemplate().exchange(url, HttpMethod.GET, entity, String.class);
+    }
+
+    static String readRandomStringFromFile() throws IOException {
+        BufferedReader reader = new BufferedReader(new FileReader("src/test/resources/randomSringForheader.txt"));
+        StringBuilder stringBuilder = new StringBuilder();
+        String line = null;
+        String ls = System.getProperty("line.separator");
+        while ((line = reader.readLine()) != null) {
+            stringBuilder.append(line);
+            stringBuilder.append(ls);
+        }
+        stringBuilder.deleteCharAt(stringBuilder.length() - 1);
+        reader.close();
+        String content = stringBuilder.toString();
+        return content;
+    }
+
+}