Implement #20 to some degree

release-notes/VERSION

@@ -3,6 +3,8 @@ Version: 2.3.0 (xx-xxx-2013)
 
 #11: Default `CsvMapper` to use alphabetic sorting of properties (since
  alternative is basically undefined; and with JDK 1.7+, unstable too)
+#20: Support filtering (`@JsonView`, `@JsonFilter`) with CSV
+ (requested by mablaev@github)
 - Add support for `JsonGenerator.Feature.WRITE_BIGDECIMAL_AS_PLAIN`
 
 ------------------------------------------------------------------------

src/main/java/com/fasterxml/jackson/dataformat/csv/CsvGenerator.java

@@ -9,7 +9,6 @@
 import com.fasterxml.jackson.core.base.GeneratorBase;
 import com.fasterxml.jackson.core.json.JsonWriteContext;
 import com.fasterxml.jackson.core.io.IOContext;
-
 import com.fasterxml.jackson.dataformat.csv.impl.CsvWriter;
 
 public class CsvGenerator extends GeneratorBase
@@ -158,11 +157,6 @@ public CsvGenerator setPrettyPrinter(PrettyPrinter pp) {
     public Object getOutputTarget() {
         return _writer.getOutputTarget();
     }
-
-    @Override
-    public boolean canUseSchema(FormatSchema schema) {
-        return (schema instanceof CsvSchema);
-    }
 
     @Override
     public void setSchema(FormatSchema schema)
@@ -177,6 +171,23 @@ public void setSchema(FormatSchema schema)
         }
     }
 
+    /*
+    /**********************************************************
+    /* Public API, capability introspection methods
+    /**********************************************************
+     */
+
+    @Override
+    public boolean canUseSchema(FormatSchema schema) {
+        return (schema instanceof CsvSchema);
+    }
+
+    @Override
+    public boolean canOmitFields() {
+        // Nope: CSV requires at least a placeholder
+        return false;
+    }
+
     /*
     /**********************************************************************
     /* Overridden methods; writing field names
@@ -537,6 +548,34 @@ public void writeNumber(String encodedValue) throws IOException,JsonGenerationEx
         _verifyValueWrite("write number");
         _writer.write(_columnIndex(), encodedValue);
     }
+
+    /*
+    /**********************************************************
+    /* Overrides for field methods
+    /**********************************************************
+     */
+
+    @Override
+    public void writeOmittedField(String fieldName)
+        throws IOException, JsonGenerationException
+    {
+        // basically combination of "writeFieldName()" and "writeNull()"
+        if (_writeContext.writeFieldName(fieldName) == JsonWriteContext.STATUS_EXPECT_VALUE) {
+            _reportError("Can not skip a field, expecting a value");
+        }
+        // Hmmh. Should we require a match? Actually, let's use logic: if field found,
+        // assumption is we must add a placeholder; if not, we can merely ignore
+        CsvSchema.Column col = _schema.column(fieldName);
+        if (col == null) {
+            // assumed to have been removed from schema too
+        } else {
+            // and all we do is just note index to use for following value write
+            _nextColumnByName = col.getIndex();
+            // We can basically copy what 'writeNull()' does...
+            _verifyValueWrite("skip positional value due to filtering");
+            _writer.write(_columnIndex(), "");
+        }
+    }
 
     /*
     /**********************************************************

src/test/java/com/fasterxml/jackson/dataformat/csv/TestFiltering.java

@@ -0,0 +1,98 @@
+package com.fasterxml.jackson.dataformat.csv;
+
+import java.io.BufferedReader;
+import java.io.StringReader;
+import java.util.*;
+
+import com.fasterxml.jackson.annotation.*;
+import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter.FilterExceptFilter;
+import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
+
+public class TestFiltering extends ModuleTestBase
+{
+    // Classes that represent views
+    static class ViewA { }
+    static class ViewAA extends ViewA { }
+    static class ViewB { }
+    static class ViewBB extends ViewB { }
+
+    @JsonPropertyOrder({ "a", "aa", "b" })
+    static class Bean
+    {
+        @JsonView({ ViewA.class, ViewB.class })
+        public String a = "1";
+
+        @JsonView({ViewAA.class })
+        public String aa = "2";
+
+        @JsonView(ViewB.class)
+        public String b = "3";
+    }
+
+    static final String COMPANY_FILTER = "COMPANY_FILTER";
+
+    @JsonPropertyOrder({ "id", "name", "ticker" })
+    @JsonFilter(COMPANY_FILTER)
+    public static class Company {
+        public int id;
+        public String name;
+        public String ticker;
+
+        Company() { }
+        Company(int id, String name, String ticker) {
+            this.id = id;
+            this.name = name;
+            this.ticker = ticker;
+        }
+    }
+
+    /*
+    /**********************************************************
+    /* Test methods
+    /**********************************************************
+     */
+
+    public void testWithJsonView() throws Exception
+    {
+        CsvMapper mapper = mapperForCsv();
+        CsvSchema schema = mapper.schemaFor(Bean.class).withLineSeparator("\n").withHeader();
+        String actual = mapper.writer(schema).withView(ViewB.class).writeValueAsString(new Bean());
+//      System.out.println(actual);
+
+        BufferedReader br = new BufferedReader(new StringReader(actual.trim()));
+        assertEquals("a,aa,b", br.readLine());
+        assertEquals("1,,3", br.readLine());
+        assertNull(br.readLine());
+
+        // plus read back?
+        final String INPUT = "a,aa,b\n5,6,7\n";
+        Bean result = mapper.reader(Bean.class).with(schema).withView(ViewB.class).readValue(INPUT);
+        assertEquals("5", result.a);
+        // due to filtering, ought to use default
+        assertEquals("2", result.aa);
+        assertEquals("7", result.b);
+    }
+
+    public void testWithJsonFilter() throws Exception
+    {
+        CsvMapper mapper = mapperForCsv();
+        CsvSchema schema = mapper.schemaFor(Company.class).withLineSeparator("\n").withHeader();
+
+        SimpleFilterProvider filterProvider = new SimpleFilterProvider()
+                .addFilter(COMPANY_FILTER, FilterExceptFilter.filterOutAllExcept("name", "ticker"));
+
+        List<Company> companies = Arrays.asList(
+                new Company(1, "name1", "ticker1")
+                , new Company(2, "name2", "ticker2")
+                , new Company(3, "name3", "ticker3"));
+        String actual = mapper.writer(filterProvider).withSchema(schema).writeValueAsString(companies);
+//        System.out.println(actual);
+
+        BufferedReader br = new BufferedReader(new StringReader(actual.trim()));
+        assertEquals("id,name,ticker", br.readLine());
+        assertEquals(",name1,ticker1", br.readLine());
+        assertEquals(",name2,ticker2", br.readLine());
+        assertEquals(",name3,ticker3", br.readLine());
+        assertNull(br.readLine());
+    }    
+}