svn-gvsig-desktop / trunk / libraries / libGDBMS / src / com / hardcode / gdbms / engine / ProjectionDataSource.java @ 538
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| 1 | 466 | fernando | package com.hardcode.gdbms.engine; |
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| 2 | |||
| 3 | import com.hardcode.gdbms.engine.data.DataSource; |
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| 4 | import com.hardcode.gdbms.engine.data.DriverException; |
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| 5 | import com.hardcode.gdbms.engine.data.ReadDriver; |
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| 6 | import com.hardcode.gdbms.engine.instruction.Expression; |
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| 7 | import com.hardcode.gdbms.engine.instruction.FieldNotFoundException; |
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| 8 | import com.hardcode.gdbms.engine.instruction.SemanticException; |
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| 9 | import com.hardcode.gdbms.engine.values.Value; |
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| 10 | |||
| 11 | |||
| 12 | /**
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| 13 | * DataSource que a?ade caracter?sticas de proyecci?n sobre campos al
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| 14 | * DataSource subyacente.
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| 15 | *
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| 16 | * @author Fernando Gonz?lez Cort?s
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| 17 | */
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| 18 | public class ProjectionDataSource implements DataSource { |
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| 19 | private DataSource source; |
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| 20 | private Expression[] fields; |
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| 21 | private String[] aliases; |
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| 22 | |||
| 23 | /**
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| 24 | * Creates a new ProjectionDataSource object.
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| 25 | *
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| 26 | * @param source DataSource origen de la informaci?n
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| 27 | * @param fields Con los ?ndices de los campos proyectados
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| 28 | * @param aliases Nombres asignados en la instrucci?n a los campos
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| 29 | */
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| 30 | public ProjectionDataSource(DataSource source, Expression[] fields, |
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| 31 | String[] aliases) { |
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| 32 | this.source = source;
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| 33 | this.fields = fields;
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| 34 | this.aliases = aliases;
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| 35 | } |
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| 36 | |||
| 37 | /**
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| 38 | * Dado el ?ndice de un campo en la tabla proyecci?n, se devuelve el ?ndice
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| 39 | * real en el DataSource subyacente
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| 40 | *
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| 41 | * @param index ?ndice del campo cuyo ?ndice en el DataSource subyacente se
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| 42 | * quiere obtener
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| 43 | *
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| 44 | * @return ?ndice del campo en el DataSource subyacente
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| 45 | */
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| 46 | private Expression getFieldByIndex(int index) { |
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| 47 | return fields[index];
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| 48 | } |
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| 49 | |||
| 50 | /**
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| 51 | * @see com.hardcode.gdbms.data.DataSource#
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| 52 | */
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| 53 | public void stop() throws DriverException { |
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| 54 | source.stop(); |
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| 55 | } |
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| 56 | |||
| 57 | /**
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| 58 | * @see com.hardcode.gdbms.data.DataSource#
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| 59 | */
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| 60 | public int getFieldCount() throws DriverException { |
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| 61 | return fields.length;
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| 62 | } |
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| 63 | |||
| 64 | /**
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| 65 | * @see com.hardcode.gdbms.data.DataSource#
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| 66 | */
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| 67 | public int getFieldIndexByName(String fieldName) |
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| 68 | throws DriverException, FieldNotFoundException {
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| 69 | /*
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| 70 | * Se comprueba si dicho ?ndice est? mapeado o la ProjectionDataSource
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| 71 | * no lo tiene
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| 72 | */
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| 73 | for (int i = 0; i < fields.length; i++) { |
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| 74 | if (fieldName.compareTo(fields[i].getFieldName()) == 0) { |
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| 75 | return i;
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| 76 | } |
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| 77 | } |
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| 78 | |||
| 79 | throw new FieldNotFoundException(); |
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| 80 | } |
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| 81 | |||
| 82 | /**
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| 83 | * @see com.hardcode.gdbms.data.DataSource#
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| 84 | */
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| 85 | public String getFieldName(int fieldId) throws DriverException { |
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| 86 | if (aliases[fieldId] != null) { |
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| 87 | return aliases[fieldId];
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| 88 | } else {
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| 89 | String name = fields[fieldId].getFieldName();
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| 90 | |||
| 91 | if (name == null) { |
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| 92 | return "unknown" + fieldId; |
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| 93 | } else {
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| 94 | return name;
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| 95 | } |
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| 96 | } |
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| 97 | } |
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| 98 | |||
| 99 | /**
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| 100 | * @see com.hardcode.gdbms.data.DataSource#
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| 101 | */
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| 102 | public Value getFieldValue(long rowIndex, int fieldId) |
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| 103 | throws DriverException {
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| 104 | try {
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| 105 | return getFieldByIndex(fieldId).evaluate(rowIndex);
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| 106 | } catch (SemanticException e) {
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| 107 | throw new DriverException(e); |
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| 108 | } |
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| 109 | } |
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| 110 | |||
| 111 | /**
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| 112 | * @see com.hardcode.gdbms.data.DataSource#
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| 113 | */
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| 114 | public long getRowCount() throws DriverException { |
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| 115 | return source.getRowCount();
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| 116 | } |
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| 117 | |||
| 118 | /**
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| 119 | * @see com.hardcode.gdbms.data.DataSource#
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| 120 | */
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| 121 | public void start() throws DriverException { |
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| 122 | source.start(); |
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| 123 | } |
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| 124 | |||
| 125 | /**
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| 126 | * @see com.hardcode.gdbms.engine.data.DataSource#getName()
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| 127 | */
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| 128 | public String getName() { |
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| 129 | return ""; |
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| 130 | } |
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| 131 | |||
| 132 | /**
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| 133 | * @see com.hardcode.gdbms.engine.data.DataSource#getDBMS()
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| 134 | */
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| 135 | public String getDBMS() { |
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| 136 | return source.getDBMS();
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| 137 | } |
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| 138 | |||
| 139 | /**
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| 140 | * @see com.hardcode.gdbms.engine.data.DataSource#getDriver()
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| 141 | */
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| 142 | public ReadDriver getDriver() {
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| 143 | return null; |
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| 144 | } |
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| 145 | } |