500 Internal Server Error Prevention Checklist

This comprehensive checklist helps prevent 500 Internal Server Errors and Java exceptions in the IoTBay web application. Use this checklist during pre-deployment QA and CI/CD pipeline validation.

Quick Start - Automated Validation:

.\scripts\validate-500-prevention.ps1 -Verbose

This will automatically check many items in this checklist. See scripts/README.md for details.

Priority Levels:

ðŸ”´ Critical: Must be checked before any deployment
ðŸŸ High: Should be verified in most deployments
ðŸŸ¡ Medium: Recommended for production deployments
ðŸŸ¢ Low: Best practice improvements

1. Backend Code Stability

Null Pointer Prevention

ðŸ”´ All method parameters are null-checked before use
ðŸ”´ All database query results are null-checked before accessing fields
ðŸ”´ Session attributes are null-checked before casting (e.g., session.getAttribute("user"))
ðŸ”´ Request parameters are validated before use (use SecurityUtil.getValidatedStringParameter())
ðŸ”´ Collection operations check for null collections before iteration
ðŸŸ Optional values use Optional<T> or explicit null checks
ðŸŸ¡ String operations check for null/empty before equals(), contains(), etc.

Example Pattern:

User user = (User) session.getAttribute("user");
if (user == null) {
    response.sendRedirect("/login.jsp");
    return;
}

Resource Management

ðŸ”´ All database connections use try-with-resources or are properly closed in finally blocks
ðŸ”´ PreparedStatement objects are closed (preferably via try-with-resources)
ðŸ”´ ResultSet objects are closed (preferably via try-with-resources)
ðŸ”´ File streams (InputStream, OutputStream) are closed properly
ðŸ”´ Connection pool connections are returned to pool after use
ðŸŸ Verify ConnectionPool.releaseConnection() is called in all code paths
ðŸŸ¡ Check for connection leaks in long-running operations

Current Pattern (Good):

try (PreparedStatement statement = connection.prepareStatement(query)) {
    // ... operations
}

Input Validation

ðŸ”´ All user inputs are validated using SecurityUtil.getValidatedStringParameter()
ðŸ”´ Numeric inputs use SecurityUtil.getValidatedIntParameter() or getValidatedDoubleParameter()
ðŸ”´ Input length limits are enforced (e.g., email max 100 chars, name max 50 chars)
ðŸ”´ Email format validation using ValidationUtil.validateEmail()
ðŸ”´ Password strength validation using SecurityUtil.isStrongPassword()
ðŸ”´ Date format validation with proper exception handling
ðŸŸ Input sanitization using SecurityUtil.sanitizeInput() for display
ðŸŸ¡ SQL injection prevention: all queries use PreparedStatement (never string concatenation)

Example Pattern:

String email = SecurityUtil.getValidatedStringParameter(request, "email", 100);
if (email == null) {
    ErrorAction.handleValidationError(request, response, "Email is required", "ControllerName");
    return;
}

Type Safety and Casting

ðŸ”´ All casts are checked with instanceof before casting
ðŸ”´ Session attribute casts are validated (e.g., User from session)
ðŸ”´ Number parsing (Integer.parseInt, Double.parseDouble) wrapped in try-catch
ðŸŸ Generic types are properly parameterized (no raw types)
ðŸŸ¡ Avoid unsafe casts; use type-safe alternatives where possible

Example Pattern:

Object userObj = session.getAttribute("user");
if (userObj instanceof User) {
    User user = (User) userObj;
    // ... use user
}

Collection Handling

ðŸ”´ Collections are initialized before use (avoid NullPointerException)
ðŸ”´ Iteration checks for null elements in collections
ðŸ”´ ConcurrentModificationException prevention: use iterator or concurrent collections
ðŸŸ Empty collections return empty list/map, not null
ðŸŸ¡ Large collections use pagination to prevent memory issues

Thread Safety

ðŸŸ Shared mutable state is synchronized or uses thread-safe collections
ðŸŸ Static variables are thread-safe or properly synchronized
ðŸŸ¡ ConnectionPool singleton pattern is thread-safe (verified)

2. Error Handling & Exception Management

Try-Catch Coverage

ðŸ”´ All database operations wrapped in try-catch blocks
ðŸ”´ All servlet doGet/doPost methods have catch-all exception handlers
ðŸ”´ File I/O operations have exception handling
ðŸ”´ JSON parsing operations (Gson) have exception handling
ðŸŸ Network operations (if any) have timeout and exception handling
ðŸŸ¡ All public methods that can throw checked exceptions document them

Example Pattern:

try {
    // ... operation
} catch (SQLException e) {
    ErrorAction.handleDatabaseError(request, response, e, "ControllerName.methodName");
} catch (Exception e) {
    ErrorAction.handleServerError(request, response, e, "ControllerName.methodName");
}

Exception Hierarchy and Custom Exceptions

ðŸŸ¡ Custom exceptions extend appropriate base exceptions
ðŸŸ¡ Exceptions include contextual information (user ID, operation, etc.)
ðŸŸ¢ Exception messages don't expose sensitive information

Error Response Handling

ðŸ”´ All errors use ErrorAction utility methods (not direct error responses)
ðŸ”´ Generic error messages returned to clients (no stack traces)
ðŸ”´ Proper HTTP status codes set (400, 401, 403, 500, etc.)
ðŸ”´ Error page forwarding has fallback to sendError() if forwarding fails
ðŸŸ JSON API endpoints return consistent error format
ðŸŸ¡ Error responses include request ID for tracking (if implemented)

Current Pattern (Good):

ErrorAction.handleDatabaseError(request, response, e, "ControllerName.methodName");

Graceful Degradation

ðŸŸ Non-critical operations fail gracefully without breaking main flow
ðŸŸ Access log failures don't prevent user operations
ðŸŸ¡ Feature flags or fallbacks for optional features

ErrorAction Utility Usage Verification

ðŸ”´ Database errors use ErrorAction.handleDatabaseError()
ðŸ”´ Validation errors use ErrorAction.handleValidationError()
ðŸ”´ Authentication errors use ErrorAction.handleAuthenticationError()
ðŸ”´ Authorization errors use ErrorAction.handleAuthorizationError()
ðŸ”´ Server errors use ErrorAction.handleServerError()
ðŸŸ Missing parameters use ErrorAction.handleMissingParameterError()
ðŸŸ Invalid input uses ErrorAction.handleInvalidInputError()

3. Database & Data Access

Connection Pooling and Management

ðŸ”´ ConnectionPool is properly initialized before use
ðŸ”´ Connections are obtained from pool (not direct DriverManager)
ðŸ”´ Connections are returned to pool in finally blocks
ðŸ”´ Connection pool size is appropriate for expected load (currently 10)
ðŸŸ Connection pool monitoring/logging for pool exhaustion
ðŸŸ¡ Connection pool configuration is externalized (not hardcoded)

Current Implementation:

ConnectionPool with size 10
DBConnection for direct connections (verify usage)

SQL Injection Prevention

ðŸ”´ All SQL queries use PreparedStatement (never string concatenation)
ðŸ”´ All user inputs are parameterized (no direct SQL string building)
ðŸ”´ Dynamic SQL queries (if any) use whitelist validation
ðŸŸ¡ SQL query patterns reviewed for injection vulnerabilities

Current Pattern (Good):

String query = "SELECT * FROM Users WHERE email = ?";
try (PreparedStatement statement = connection.prepareStatement(query)) {
    statement.setString(1, email);
    // ...
}

Transaction Handling

ðŸŸ Multi-step operations use transactions where appropriate
ðŸŸ Transaction rollback on errors
ðŸŸ¡ Transaction timeout configuration

ResultSet and PreparedStatement Cleanup

ðŸ”´ All ResultSet objects use try-with-resources
ðŸ”´ All PreparedStatement objects use try-with-resources
ðŸ”´ Nested try-with-resources properly structured
ðŸŸ ResultSet iteration checks rs.next() before accessing columns

Current Pattern (Good):

try (PreparedStatement statement = connection.prepareStatement(query);
     ResultSet rs = statement.executeQuery()) {
    while (rs.next()) {
        // ... process results
    }
}

Database Connection Timeout Handling

ðŸŸ Connection timeout configured in connection string or properties
ðŸŸ Query timeout set on PreparedStatement for long-running queries
ðŸŸ¡ Connection retry logic for transient failures

SQLite-Specific Considerations

ðŸ”´ SQLite database file path is correct and writable
ðŸ”´ SQLite database file permissions are set correctly
ðŸŸ SQLite WAL mode enabled for better concurrency (if needed)
ðŸŸ SQLite connection limits understood (SQLite has limited concurrent writes)
ðŸŸ¡ Database file backup strategy in place
ðŸŸ¡ Database file size monitoring (SQLite can grow large)

Current Configuration:

Database: jdbc:sqlite:iotbay.db
Driver: org.sqlite.JDBC

4. Logging & Monitoring

Logger Configuration

ðŸ”´ All classes use Logger.getLogger(ClassName.class.getName())
ðŸ”´ Logger instances are static final
ðŸŸ Logging configuration file (logging.properties) exists and is configured
ðŸŸ¡ Log levels appropriate for production (INFO/WARNING/SEVERE, not FINE/FINER)

Current Pattern:

private static final Logger logger = Logger.getLogger(ClassName.class.getName());

Log Levels and Appropriate Usage

ðŸ”´ SEVERE: Used for exceptions and critical errors
ðŸŸ WARNING: Used for validation errors, security events, recoverable issues
ðŸŸ INFO: Used for important business events (user login, order creation)
ðŸŸ¡ FINE/FINER: Used for debugging (disabled in production)

Example Pattern:

logger.log(Level.SEVERE, "Database error in context", e);
logger.warning("Validation error: " + errorMessage);
logger.info("User logged in: " + email);

Exception Stack Trace Logging

ðŸ”´ All caught exceptions log full stack trace with logger.log(Level.SEVERE, message, exception)
ðŸ”´ Contextual information included in log messages (IP, user, operation)
ðŸŸ ErrorAction methods log detailed information for administrators
ðŸŸ¡ Stack traces never exposed to end users (only in logs)

Current Pattern (Good):

logger.log(Level.SEVERE, 
    String.format("[DATABASE_ERROR] Context: %s, IP: %s", logContext, getClientIP(request)), 
    e);

Contextual Information in Logs

ðŸŸ Logs include request context (IP address, user, endpoint)
ðŸŸ Logs include operation context (method name, parameters)
ðŸŸ¡ Request ID or correlation ID for tracing (if implemented)
ðŸŸ¡ User ID included in security-relevant logs

Log File Rotation and Management

ðŸŸ¡ Log file rotation configured (size-based or time-based)
ðŸŸ¡ Log file retention policy defined
ðŸŸ¡ Log file location is writable and has sufficient disk space
ðŸŸ¢ Log aggregation/monitoring tool configured (if available)

Production vs Development Logging

ðŸŸ¡ Development: More verbose logging enabled
ðŸŸ¡ Production: Sensitive information not logged (passwords, tokens)
ðŸŸ¡ Production: Log levels set to INFO/WARNING/SEVERE
ðŸŸ¢ Environment-specific logging configuration

5. Deployment & Build Configuration

Maven Build Validation

ðŸ”´ mvn clean compile succeeds without errors
ðŸ”´ mvn clean package creates valid WAR file
ðŸ”´ No compilation warnings (or warnings are acceptable and documented)
ðŸŸ mvn test passes all unit tests
ðŸŸ¡ Dependency versions are compatible (no conflicts)
ðŸŸ¡ Maven build is reproducible (same output on different machines)

Current Configuration:

Java 8 (1.8)
Maven compiler plugin 3.11.0
WAR packaging

WAR File Integrity

ðŸ”´ WAR file is properly structured (WEB-INF/classes, WEB-INF/lib, etc.)
ðŸ”´ All required classes are included in WAR
ðŸ”´ All dependencies are included in WEB-INF/lib
ðŸ”´ web.xml is valid and properly formatted
ðŸŸ WAR file size is reasonable (check for unnecessary files)
ðŸŸ¡ WAR file can be extracted and inspected

Configuration File Validation

ðŸ”´ application.properties exists and is readable
ðŸ”´ Database connection properties are correct
ðŸ”´ All required properties have values (no null/empty)
ðŸŸ Environment-specific properties validated (dev/staging/prod)
ðŸŸ¡ Configuration file encoding is UTF-8

Current Properties:

db.url, db.driver
security.session.timeout, security.password.min.length, security.max.login.attempts
app.name, app.version, app.environment

Environment-Specific Settings

ðŸŸ Database URL points to correct environment
ðŸŸ Log levels appropriate for environment
ðŸŸ Error page behavior appropriate (dev shows details, prod generic)
ðŸŸ¡ Feature flags set correctly per environment

Dependency Version Compatibility

ðŸŸ¡ All dependencies are compatible with Java 8
ðŸŸ¡ Servlet API version compatible with server (3.1.0)
ðŸŸ¡ JSTL version compatible (1.2)
ðŸŸ¡ SQLite JDBC driver version is stable (3.49.1.0)
ðŸŸ¢ No known security vulnerabilities in dependencies

Current Dependencies:

javax.servlet-api 3.1.0
sqlite-jdbc 3.49.1.0
gson 2.10.1
JSTL 1.2

Classpath and Resource Loading

ðŸ”´ application.properties is in classpath (src/main/resources)
ðŸ”´ JSP files are in correct location (src/main/webapp)
ðŸ”´ Static resources (CSS, JS, images) are accessible
ðŸŸ Resource files use UTF-8 encoding
ðŸŸ¡ External resources (if any) are accessible from server

6. Server Configuration (Tomcat/Jetty)

JVM Memory Settings

ðŸ”´ Heap size configured appropriately (-Xmx, -Xms)
ðŸ”´ Metaspace/PermGen configured for Java 8 (-XX:MetaspaceSize, -XX:MaxMetaspaceSize)
ðŸŸ OutOfMemoryError handling strategy defined
ðŸŸ¡ Heap dump configuration for OOM debugging
ðŸŸ¡ Memory monitoring enabled

Recommended Settings:

-Xmx512m -Xms256m (adjust based on application needs)
-XX:MetaspaceSize=128m -XX:MaxMetaspaceSize=256m (Java 8)

Thread Pool Configuration

ðŸŸ Max threads configured appropriately for expected load
ðŸŸ Min spare threads configured
ðŸŸ¡ Thread timeout configured
ðŸŸ¡ Thread pool monitoring enabled

Jetty Configuration (Development):

Port: 8080
Context path: /

Connection Timeout Settings

ðŸŸ Connection timeout configured (default 20000ms)
ðŸŸ Keep-alive timeout configured
ðŸŸ¡ Request timeout configured for long-running requests

Session Management

ðŸ”´ Session timeout configured (currently 30 minutes from application.properties)
ðŸ”´ Session persistence configured (if needed)
ðŸŸ Session cookie security settings (HttpOnly, Secure in production)
ðŸŸ¡ Session size monitoring (prevent memory issues)

Current Configuration:

security.session.timeout=30 (minutes)

Error Page Configuration

ðŸ”´ Error pages configured in web.xml (400, 404, 500, Exception)
ðŸ”´ Error pages exist and are accessible
ðŸ”´ Error pages don't expose sensitive information
ðŸŸ Custom error pages for different error types (if needed)

Current Configuration:

<error-page>
    <error-code>500</error-code>
    <location>/error.jsp</location>
</error-page>
<error-page>
    <exception-type>java.lang.Exception</exception-type>
    <location>/error.jsp</location>
</error-page>

Context Path and Deployment Settings

ðŸ”´ Context path is correct (currently /)
ðŸ”´ WAR file name matches expected deployment name
ðŸŸ Auto-deploy settings appropriate for environment
ðŸŸ¡ Deployment descriptor (web.xml) is valid

7. Java Runtime Environment

Java Version Compatibility

ðŸ”´ Java version matches build target (Java 8 / 1.8)
ðŸ”´ Server Java version is compatible with application
ðŸŸ Java version is stable (not EOL or beta)
ðŸŸ¡ JAVA_HOME is set correctly on server

Current Target:

Java 8 (1.8)
Maven compiler: release 8

JVM Arguments and Tuning

ðŸŸ GC algorithm selected appropriately (G1GC recommended for Java 8+)
ðŸŸ GC logging enabled for production monitoring
ðŸŸ¡ JVM tuning based on application profiling
ðŸŸ¢ JVM crash logs location configured

Recommended JVM Args:

-XX:+UseG1GC (G1 Garbage Collector)
-XX:+PrintGCDetails -Xloggc:/path/to/gc.log (GC logging)

Garbage Collection Settings

ðŸŸ¡ GC pause time targets set (if using G1GC)
ðŸŸ¡ GC heap regions configured (if using G1GC)
ðŸŸ¢ GC monitoring and alerting configured

Class Loading Issues

ðŸŸ ClassNotFoundException/NoClassDefFoundError prevention
ðŸŸ Classpath is correct and complete
ðŸŸ¡ Class loading order issues resolved
ðŸŸ¢ Class loader leaks monitored

Reflection and Security Manager

ðŸŸ¡ Reflection usage is safe (no arbitrary code execution)
ðŸŸ¡ Security manager policies configured (if enabled)
ðŸŸ¢ Reflection performance impact assessed

8. Pre-Deployment QA Checklist

Code Review Items

ðŸ”´ All critical and high-priority items from above sections checked
ðŸ”´ Code review completed by at least one other developer
ðŸŸ Security review completed (especially for authentication/authorization)
ðŸŸ¡ Code style and best practices followed
ðŸŸ¡ No TODO/FIXME comments in critical paths

Testing Requirements

ðŸ”´ Unit tests pass (if available)
ðŸ”´ Integration tests pass (if available)
ðŸ”´ Manual testing of critical user flows completed
ðŸ”´ Error scenarios tested (invalid input, missing data, etc.)
ðŸŸ Performance testing completed (if applicable)
ðŸŸ Load testing completed (if applicable)
ðŸŸ¡ Edge cases tested

Performance Testing

ðŸŸ Response times meet requirements
ðŸŸ Database query performance acceptable
ðŸŸ Memory usage within limits
ðŸŸ¡ No memory leaks detected
ðŸŸ¡ Connection pool sizing validated under load

Security Validation

ðŸ”´ SQL injection prevention verified
ðŸ”´ XSS prevention verified (input sanitization)
ðŸ”´ Authentication and authorization working correctly
ðŸ”´ Session management secure
ðŸŸ Password handling secure (hashing, not plaintext)
ðŸŸ¡ CSRF protection (if implemented)
ðŸŸ¡ Rate limiting working (if implemented)

Configuration Review

ðŸ”´ All configuration files reviewed
ðŸ”´ Environment-specific settings verified
ðŸŸ Configuration values are reasonable (timeouts, limits, etc.)
ðŸŸ¡ Configuration is externalized (not hardcoded)
ðŸŸ¡ Configuration changes documented

9. CI/CD Pipeline Validation

Automated Test Execution

ðŸ”´ Unit tests run automatically in CI pipeline
ðŸ”´ Integration tests run automatically in CI pipeline
ðŸŸ Test failures block deployment
ðŸŸ¡ Test coverage meets minimum threshold (if defined)
ðŸŸ¡ Test results are reported and visible

Build Verification

ðŸ”´ Maven build runs successfully in CI environment
ðŸ”´ WAR file is created and validated
ðŸŸ Build artifacts are stored/archived
ðŸŸ¡ Build time is acceptable
ðŸŸ¡ Build is reproducible

Static Code Analysis

ðŸŸ Static analysis tools run (FindBugs, PMD, Checkstyle, SonarQube)
ðŸŸ Critical and high-severity issues resolved
ðŸŸ¡ Code quality metrics meet thresholds
ðŸŸ¡ Technical debt tracked

Dependency Vulnerability Scanning

ðŸŸ Dependency vulnerability scan runs (OWASP Dependency-Check, Snyk)
ðŸŸ High/critical vulnerabilities resolved or documented
ðŸŸ¡ Dependency updates reviewed regularly
ðŸŸ¡ Security advisories monitored

Deployment Smoke Tests

ðŸ”´ Application starts successfully after deployment
ðŸ”´ Health check endpoint responds (if available)
ðŸ”´ Database connection works
ðŸ”´ Critical endpoints are accessible
ðŸŸ Error pages work correctly
ðŸŸ¡ Logging is working
ðŸŸ¡ Performance is acceptable

Suggested Smoke Test Endpoints:

/ (home page)
/api/login (authentication)
/error.jsp (error handling)

10. Runtime Monitoring & Alerting

Health Check Endpoints

ðŸŸ¡ Health check endpoint implemented (if applicable)
ðŸŸ¡ Health check verifies database connectivity
ðŸŸ¡ Health check verifies critical dependencies
ðŸŸ¢ Health check used by load balancer/monitoring

Error Rate Monitoring

ðŸŸ 500 error rate is monitored
ðŸŸ Error rate alerts configured (threshold-based)
ðŸŸ¡ Error trends tracked over time
ðŸŸ¡ Error categorization (database, validation, server, etc.)

Performance Metrics

ðŸŸ Response time monitoring enabled
ðŸŸ Request throughput monitoring
ðŸŸ¡ Database query performance monitored
ðŸŸ¡ Memory usage monitored
ðŸŸ¡ CPU usage monitored

Alert Thresholds

ðŸŸ Alert thresholds defined for critical metrics
ðŸŸ Alert recipients configured
ðŸŸ¡ Alert escalation process defined
ðŸŸ¡ False positive reduction (alert tuning)

Suggested Alert Thresholds:

500 error rate > 1% of requests
Response time > 2 seconds (p95)
Memory usage > 80%
Database connection pool exhaustion

Quick Reference: Common 500 Error Causes

Database-Related

SQLException: Check connection, query syntax, database availability
NullPointerException in DAO: Check null handling for query results
Connection pool exhaustion: Check connection release in finally blocks

Servlet-Related

NullPointerException: Check session attributes, request parameters
ClassCastException: Check instanceof before casting session attributes
ServletException: Check servlet initialization, web.xml configuration

Configuration-Related

Missing configuration properties: Check application.properties
Invalid database URL: Check db.url property
Missing dependencies: Check WEB-INF/lib in WAR file

Resource-Related

OutOfMemoryError: Check JVM heap settings, memory leaks
FileNotFoundException: Check file paths, permissions
IOException: Check file I/O operations, network operations

Checklist Usage

Automated Validation

Quick Start:

# Run automated validation script
.\scripts\validate-500-prevention.ps1 -Verbose

The automated validation script checks many items automatically:

Null pointer prevention patterns
Resource management (try-with-resources)
Error handling patterns
SQL injection prevention
Logging configuration
Configuration file validation
Build configuration
Error page configuration

See scripts/README.md for details.

Pre-Deployment

Run automated validation script (see above)
Review all Critical (ðŸ”´) items manually
Review all High (ðŸŸ ) items relevant to your changes
Complete manual testing
Run automated tests
Verify configuration

CI/CD Integration

Add validation script to pipeline (see scripts/README.md)
Automate Critical items where possible
Include High-priority checks in pipeline
Generate reports from checklist results

Example CI/CD Integration:

- name: Validate 500 Error Prevention
  run: pwsh -File scripts/validate-500-prevention.ps1 -Verbose

Post-Incident Review

Use checklist to identify root cause
Add new items based on incident learnings
Update priorities based on actual issues
Update validation script with new patterns

Notes

This checklist is specific to the IoTBay application architecture
Update checklist as application evolves
Share learnings and improvements with team
Regular review and update of checklist items

Last Updated: 2025-01-XX Application Version: 1.0.0 Java Version: 8 (1.8) Server: Jetty (dev) / Tomcat (prod)

Document Version: 1.0.0 Status: Published Last Updated: 12¿ù 3, 2025 Audience: Developers, Stakeholders Maintained By: IoT Bay Documentation Team

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500 Internal Server Error Prevention Checklist

1. Backend Code Stability

Null Pointer Prevention

Resource Management

Input Validation

Type Safety and Casting

Collection Handling

Thread Safety

2. Error Handling & Exception Management

Try-Catch Coverage

Exception Hierarchy and Custom Exceptions

Error Response Handling

Graceful Degradation

ErrorAction Utility Usage Verification

3. Database & Data Access

Connection Pooling and Management

SQL Injection Prevention

Transaction Handling

ResultSet and PreparedStatement Cleanup

Database Connection Timeout Handling

SQLite-Specific Considerations

4. Logging & Monitoring

Logger Configuration

Log Levels and Appropriate Usage

Exception Stack Trace Logging

Contextual Information in Logs

Log File Rotation and Management

Production vs Development Logging

5. Deployment & Build Configuration

Maven Build Validation

WAR File Integrity

Configuration File Validation

Environment-Specific Settings

Dependency Version Compatibility

Classpath and Resource Loading

6. Server Configuration (Tomcat/Jetty)

JVM Memory Settings

Thread Pool Configuration

Connection Timeout Settings

Session Management

Error Page Configuration

Context Path and Deployment Settings

7. Java Runtime Environment

Java Version Compatibility

JVM Arguments and Tuning

Garbage Collection Settings

Class Loading Issues

Reflection and Security Manager

8. Pre-Deployment QA Checklist

Code Review Items

Testing Requirements

Performance Testing

Security Validation

Configuration Review

9. CI/CD Pipeline Validation

Automated Test Execution

Build Verification

Static Code Analysis

Dependency Vulnerability Scanning

Deployment Smoke Tests

10. Runtime Monitoring & Alerting

Health Check Endpoints

Error Rate Monitoring

Performance Metrics

Alert Thresholds

Quick Reference: Common 500 Error Causes

Database-Related

Servlet-Related

Configuration-Related

Resource-Related

Checklist Usage

Automated Validation

Pre-Deployment

CI/CD Integration