diff --git a/src/main/java/org/itsallcode/jdbc/dialect/ColumnValueSetter.java b/src/main/java/org/itsallcode/jdbc/dialect/ColumnValueSetter.java
index a124cbd..98765fe 100644
--- a/src/main/java/org/itsallcode/jdbc/dialect/ColumnValueSetter.java
+++ b/src/main/java/org/itsallcode/jdbc/dialect/ColumnValueSetter.java
@@ -3,7 +3,21 @@
 import java.sql.PreparedStatement;
 import java.sql.SQLException;
 
+/**
+ * Implementors of this interface optionally convert an object and set it on a
+ * {@link PreparedStatement}.
+ * 
+ * @param <T> object type
+ */
 public interface ColumnValueSetter<T> {
 
+    /**
+     * Optionally convert an object and set it on a {@link PreparedStatement}.
+     * 
+     * @param stmt           prepared statement
+     * @param parameterIndex parameter index
+     * @param object         object to convert
+     * @throws SQLException if setting fails
+     */
     void setObject(PreparedStatement stmt, int parameterIndex, T object) throws SQLException;
 }
diff --git a/src/main/java/org/itsallcode/jdbc/dialect/DbDialect.java b/src/main/java/org/itsallcode/jdbc/dialect/DbDialect.java
index dfc0b7b..3a5be6e 100644
--- a/src/main/java/org/itsallcode/jdbc/dialect/DbDialect.java
+++ b/src/main/java/org/itsallcode/jdbc/dialect/DbDialect.java
@@ -23,5 +23,13 @@ public interface DbDialect {
      */
     ColumnValueExtractor createExtractor(final ColumnMetaData column);
 
+    /**
+     * Create a new column value setter for setting values on a
+     * {@link java.sql.PreparedStatement} specific to the dialect.
+     * 
+     * @param <T>  object type
+     * @param type object type
+     * @return column value setter
+     */
     <T> ColumnValueSetter<T> createSetter(Class<T> type);
 }
diff --git a/src/main/java/org/itsallcode/jdbc/dialect/Setters.java b/src/main/java/org/itsallcode/jdbc/dialect/Setters.java
index 406217b..7592258 100644
--- a/src/main/java/org/itsallcode/jdbc/dialect/Setters.java
+++ b/src/main/java/org/itsallcode/jdbc/dialect/Setters.java
@@ -4,11 +4,11 @@
 import java.time.*;
 import java.time.format.DateTimeFormatter;
 
-public final class Setters {
+final class Setters {
     private Setters() {
     }
 
-    public static <T> ColumnValueSetter<T> generic() {
+    static <T> ColumnValueSetter<T> generic() {
         return PreparedStatement::setObject;
     }
 
@@ -17,13 +17,13 @@ static ColumnValueSetter<LocalDate> localDateToString() {
                 .setString(parameterIndex, date.toString());
     }
 
-    public static ColumnValueSetter<Instant> instantToString(final DateTimeFormatter dateTimeFormatter,
+    static ColumnValueSetter<Instant> instantToString(final DateTimeFormatter dateTimeFormatter,
             final ZoneId timeZone) {
         return (final PreparedStatement stmt, final int parameterIndex, final Instant instant) -> stmt
                 .setString(parameterIndex, dateTimeFormatter.format(LocalDateTime.ofInstant(instant, timeZone)));
     }
 
-    public static ColumnValueSetter<LocalDateTime> localDateTimeToString(final DateTimeFormatter dateTimeFormatter) {
+    static ColumnValueSetter<LocalDateTime> localDateTimeToString(final DateTimeFormatter dateTimeFormatter) {
         return (final PreparedStatement stmt, final int parameterIndex, final LocalDateTime localDateTime) -> stmt
                 .setString(parameterIndex, dateTimeFormatter.format(localDateTime));
     }
diff --git a/src/main/java/org/itsallcode/jdbc/statement/ConvertingPreparedStatement.java b/src/main/java/org/itsallcode/jdbc/statement/ConvertingPreparedStatement.java
index ca3a177..d4f3dea 100644
--- a/src/main/java/org/itsallcode/jdbc/statement/ConvertingPreparedStatement.java
+++ b/src/main/java/org/itsallcode/jdbc/statement/ConvertingPreparedStatement.java
@@ -3,10 +3,10 @@
 import java.sql.PreparedStatement;
 import java.sql.SQLException;
 
-
 /**
- * A {@link PreparedStatement} that delegates all methods and converts parameter
- * value of {@link #convert(Object)} using a {@link ParameterMapper}.
+ * A {@link PreparedStatement} that delegates calls to
+ * {@link #setObject(int, Object)} to a setter provided by
+ * {@link ParamSetterProvider#findSetter(Object)}.
  */
 public class ConvertingPreparedStatement extends DelegatingPreparedStatement {
     private final PreparedStatement originalDelegate;
diff --git a/src/main/java/org/itsallcode/jdbc/statement/ParamSetterProvider.java b/src/main/java/org/itsallcode/jdbc/statement/ParamSetterProvider.java
index 3edafd6..a8ea4ea 100644
--- a/src/main/java/org/itsallcode/jdbc/statement/ParamSetterProvider.java
+++ b/src/main/java/org/itsallcode/jdbc/statement/ParamSetterProvider.java
@@ -1,15 +1,26 @@
 package org.itsallcode.jdbc.statement;
 
+import java.sql.PreparedStatement;
 import java.util.HashMap;
 import java.util.Map;
 
-import org.itsallcode.jdbc.dialect.*;
+import org.itsallcode.jdbc.dialect.ColumnValueSetter;
+import org.itsallcode.jdbc.dialect.DbDialect;
 
+/**
+ * This class creates and caches {@link ColumnValueSetter} based on an object's
+ * type.
+ */
 public class ParamSetterProvider {
-    private static final ColumnValueSetter<Object> GENERIC_SETTER = Setters.generic();
+    private static final ColumnValueSetter<Object> GENERIC_SETTER = PreparedStatement::setObject;
     private final DbDialect dialect;
     private final Map<Class<?>, ColumnValueSetter<Object>> setters = new HashMap<>();
 
+    /**
+     * Create a new instance.
+     * 
+     * @param dialect database dialect
+     */
     public ParamSetterProvider(final DbDialect dialect) {
         this.dialect = dialect;
     }