github.com/apache/beam/sdks/v2@v2.48.2/java/container/pathingjar.go (about)

     1  // Licensed to the Apache Software Foundation (ASF) under one or more
     2  // contributor license agreements.  See the NOTICE file distributed with
     3  // this work for additional information regarding copyright ownership.
     4  // The ASF licenses this file to You under the Apache License, Version 2.0
     5  // (the "License"); you may not use this file except in compliance with
     6  // the License.  You may obtain a copy of the License at
     7  //
     8  //    http://www.apache.org/licenses/LICENSE-2.0
     9  //
    10  // Unless required by applicable law or agreed to in writing, software
    11  // distributed under the License is distributed on an "AS IS" BASIS,
    12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  
    16  package main
    17  
    18  import (
    19  	"archive/zip"
    20  	"fmt"
    21  	"io"
    22  	"os"
    23  	"strings"
    24  )
    25  
    26  // makePathingJar produces a context or 'pathing' jar which only contains the relative
    27  // classpaths in its META-INF/MANIFEST.MF.
    28  //
    29  // Since we build with Java 8 as a minimum, this is the only supported way of reducing
    30  // command line length, since argsfile support wasn't added until Java 9.
    31  //
    32  // https://docs.oracle.com/javase/8/docs/technotes/guides/jar/jar.html is the spec.
    33  //
    34  // In particular, we only need to populate the Jar with a Manifest-Version and Class-Path
    35  // attributes.
    36  // Per https://docs.oracle.com/javase/8/docs/technotes/guides/jar/jar.html#classpath
    37  // the classpath URLs must be relative for security reasons.
    38  func makePathingJar(classpaths []string) (string, error) {
    39  	f, err := os.Create("pathing.jar")
    40  	if err != nil {
    41  		return "", fmt.Errorf("unable to create pathing.jar: %w", err)
    42  	}
    43  	defer f.Close()
    44  	if err := writePathingJar(classpaths, f); err != nil {
    45  		return "", fmt.Errorf("unable to write pathing.jar: %w", err)
    46  	}
    47  	return f.Name(), nil
    48  }
    49  
    50  var lineBreak = []byte{'\r', '\n'}
    51  var continuation = []byte{' '}
    52  
    53  func writePathingJar(classpaths []string, w io.Writer) error {
    54  	jar := zip.NewWriter(w)
    55  	defer jar.Close()
    56  
    57  	if _, err := jar.Create("META-INF/"); err != nil {
    58  		return fmt.Errorf("unable to create META-INF/ directory: %w", err)
    59  	}
    60  
    61  	zf, err := jar.Create("META-INF/MANIFEST.MF")
    62  	if err != nil {
    63  		return fmt.Errorf("unable to create META-INF/MANIFEST.MF: %w", err)
    64  	}
    65  
    66  	zf.Write([]byte("Manifest-Version: 1.0"))
    67  	zf.Write(lineBreak)
    68  	zf.Write([]byte("Created-By: sdks/java/container/pathingjar.go"))
    69  	zf.Write(lineBreak)
    70  	// Class-Path: must have a sequence of relative URIs for the paths
    71  	// which we assume outright in this case.
    72  
    73  	// We could do this memory efficiently, but it's not worthwhile compared to the complexity
    74  	// at this stage.
    75  	allCPs := "Class-Path: file:" + strings.Join(classpaths, " file:")
    76  
    77  	const lineLenMax = 71 // it's actually 72, but we remove 1 to account for the continuation line prefix.
    78  	buf := make([]byte, lineLenMax)
    79  	cur := 0
    80  	for cur+lineLenMax < len(allCPs) {
    81  		next := cur + lineLenMax
    82  		copy(buf, allCPs[cur:next])
    83  		zf.Write(buf)
    84  		zf.Write(lineBreak)
    85  		zf.Write(continuation)
    86  		cur = next
    87  	}
    88  	zf.Write([]byte(allCPs[cur:]))
    89  	zf.Write(lineBreak)
    90  	return nil
    91  }